# How to Dose Ca and Mg



## stevenlau (Jul 21, 2009)

Hello all,

My water has both 0 dkH and dgH, so I will plan to add some calcium and magnesium to try to increase the gH up to 3 dgH but leaving the kH alone still remains 0 dkH.

Anyone please will you tell me as I am no good in chemical :

1. Which one is better CaCO3 vs CaSO4 vs CaCl2?
I read somewhere that CaCO3 will also raise kH (so I will not use this one) and CaSO4 takes too long to dissolve so I think I will pick CaCl2 but too afraid of the chloride in high amount on it. Will it be dangerous to plant and fish?

2. Will anyone please tell me how to dose (the formula/how to count) those two components (CaCl2 and MgSO4) from 0 dgH to 3 dgH?
My tank is 96 litres. At what ppm I should target those 2 components? From what I know is 10-30ppm of Ca and 2-5ppm of Mg but can I count or convert those ppm into dgH? If so, how many ppm of each Ca and Mg are for the increase of 3 dgH regarding the ratio is 4:1?

3. What is the difference between MgSO4 and MgSO4.7H2O?

Thank you very much in advance.


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## Diana K (Dec 20, 2007)

You want a ratio of more Ca than Mg, and I have heard several values. Most suggest about 4:1

I use Seachem Equilibrium or Barr's GH Booster to raise the GH in my hard water tanks. It also has a few other minerals (Potassium, iron...) that are often lacking in water that has such a low GH.

However, if you just want to target Ca and Mg, then I have heard of people using CaCl2 and there does not seem to be a problem with the chloride in the tank. MgSO4.7H2O is Epsom salt, and is a good way to dose magnesium.

Without knowing the numbers I would dose in a bucket first, with measured amounts of water and other materials. 
There are 17.9 ppm in 1 German degrees of hardness. 
So, if your test kit reports degrees, here is the goal I would aim for:
Add enough Ca (Whatever source) to raise the GH test by 4 degrees. 
Then add enough Mg to raise it by 1 more degree.

You now have in the bucket water with 4 degrees of GH from Ca, and 1 degree from Mg. This is equal to (4 x 17.9)=71.6 ppm Ca and 17.9 ppm Mg.

To translate that to the tank: The values in the bucket are about 3 times as high as you want in the tank. Dose at 1/4 of whatever you used in the bucket, then test the tank. Then you can fine tune the dose. 
Example: lets say you used 12 mg of something in the bucket, and there was 1 liter of water in the bucket. You would dose the tank at the rate of 3mg/l at first. 
This is dosing slightly less than the calculations suggest because you are not positive exactly the volume of the tank minus substrate, decorations, plus external filter volume...

http://www.aquaticplantcentral.com/forumapc/fertilator.php

This will help you figure out a ballpark amount to test in the bucket so you are not fiddling around with one granule at a time trying to find out how much of each item creates what sort of change in the water chemistry.

Looks like around 6 grams of CaCl2 added to the tank will give you a little over 20 ppm Ca, and 3 grams of Epsom salt will give you pretty close to 3 ppm Mg.


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## Philosophos (Mar 1, 2009)

CaCl2 is my favorite when I need to add a little. 

4:1 Ca:Mg is a good ratio, 5ppm Mg, 20ppm Ca is what I like to aim for if I'm working from soft/RO water.

MgSO4 is MgSO4.7H2O just about anywhere you see it; most people just shorten it up and leave out the water. Be sure to include the 7H2O in your calculations.

You'll find that by the time you've accomplished everything you need to in fertilization for a higher light tank, your GH will be taken care of anyhow.


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## Left C (Jun 14, 2005)

Make sure that you know the form of CaCl2 that you are using for your dosing calculations. Wiki lists 5 forms. 
http://en.wikipedia.org/wiki/Calcium_chloride

Molar mass 
110.98 g/mol (anhydrous)
128.999 g/mol (monohydrate)
147.014 g/mol (dihydrate)
183.045 g/mol (tetrahydrate)
219.08 g/mol (hexahydrate)


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## Diana K (Dec 20, 2007)

Maybe not so critical to know the formulas. When you measure the GH the 'other stuff' won't show up. Test in a bucket 'til you figure out how much of something creates how much change in GH.


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## Philosophos (Mar 1, 2009)

Why use a bucket and chance when you can use a scale and a little calculation? 

0.4mg/L Ca = 1ppm GH 
CaCl2 = 110.98 g/mol (most of what you get is anhydrous IME)
Ca = 40.0784 g/mol

so from there...

=110.98/40.0784*0.4
=1.107629047067747

So about 1.1ppm of CaCl2 makes for 1ppm GH, or about 19.8ppm for 1 dGH.

If you don't have a scale, you can simply take an accurate measuring cup (a small one, accurate to within a couple of ml) and add the CaCl2 with every ml increase being 2.15g. From there a couple stages of dilution should give you a nice little stock solution for giving reliable GH.

IMO though, you're better off just aiming for 20ppm Ca; that'll already put your tank around 50ppm GH.


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## stevenlau (Jul 21, 2009)

Wow, thank you very much all especially to Diana K. Now I know how to start to dose.

But before I dose, there's still something in my head, when you dose gH Booster or something else to raise both Ca and Mg or gH, do you always do it when only in WC time which is only once a week or every other day just like macro and micro?

If I target 20ppm of Ca and 5ppm of Mg, I would end up with only around 1.4 degree of hardness but if I target 4:1 ratio, I would end up in 5 dgH with 71.6ppm of Ca and 17.9ppm of Mg, right? Can I dose only once a week at WC time to raise the gH to 5dgH with 71.6ppm Ca and 17.9ppm Mg in it or should I dose them in every other day to target the 20ppm Ca and 5ppm Mg along with micro dose.

I'm dosing EI now and I usually do 50% WC once a week, so I plan to add CaCl2 and MgSO4 when I WC. Say that when I raise my gH the first time at WC time from 0 to 5 dgH and the plants will use up the Ca and Mg little by little up until the end of the week, will the change of gH from 5 to whatever degree it will end up until the end of the week could be dangerous to both fish and plant? 

Thank you very much in advance.


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## Philosophos (Mar 1, 2009)

Magnesium adds to hardness as well; it's about .2425mg to 1ppm GH:

=5/0.2425
=20.6

So that's more like 3.9 GH, maybe a touch more from any SO4 related compounds you're dosing.

I like to dose calcium and magnesium with my macros. The CaCl2 doesn't always play nice, so I like to dose it a minute or two after the macros. You can do it all at the start of the week since Ca/Mg doesn't tend to end up sequestered in non-bioavailable forms so easily as K+ or N. It's a matter of preference. 

I'm still trying to understand why you're so focused on hitting a certain number with GH, rather than focusing on the actual biological requirements of the very same elements that make GH up. You can have a GH of 12 and still have magnesium or calcium deficiencies; GH really doesn't matter in any way that I'm aware of if you understand how to provide bioavailable nutrients at the correct level. It's like asking for "food" and presuming that balanced nutrition comes with it 

If you don't believe, me ask Tom Barr for his opinion or re-read the EI guide; 50ppm GH with balanced Mg/Ca pretty much does the job unless you're keeping very specifically hard water species.


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## johnzhou2476 (Nov 28, 2006)

SteveLau, 

You are on to a good start. I suggest you read up on Kekon's posting on ca and mg. A lot of good info. I had a lot of frustation in the past and his posting help me steer in the right direction.


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## Diana K (Dec 20, 2007)

My tap water comes with 4-5 degrees GH. I have not tested to see if this is Ca or Mg. Water company report shows it is both.

I add Equilibrium to make harder water for Lake Tanganyikan fish, livebearers and a few others. I add this only once, at water change time. 
I also have coral sand and oyster shell grit in the tanks or filters, so they can help out if needed. The conditions in these tanks stays stable. 

In my soft water tanks the GH also stays stable. Topping off with tap water (in other words, dosing GH) between water changes RAISES the GH in my tanks, so I know the plants are not using enough Ca or Mg that I need to dose it per EI charts.

On the other hand, most of my tanks WILL show potassium deficiency if I do not dose plenty. I add K2SO4 for this. Equalibrium has K, but I do not need to add the Ca and Mg just to get the K. 

Test your tanks. If the GH is dropping through the week, then perhaps the plants are using so much Ca and Mg that you need to dose these materials. What works for me may not work for you.


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## stevenlau (Jul 21, 2009)

Philosophos said:


> I'm still trying to understand why you're so focused on hitting a certain number with GH, rather than focusing on the actual biological requirements of the very same elements that make GH up. You can have a GH of 12 and still have magnesium or calcium deficiencies; GH really doesn't matter in any way that I'm aware of if you understand how to provide bioavailable nutrients at the correct level. It's like asking for "food" and presuming that balanced nutrition comes with it
> 
> If you don't believe, me ask Tom Barr for his opinion or re-read the EI guide; 50ppm GH with balanced Mg/Ca pretty much does the job unless you're keeping very specifically hard water species.


Whoa, it's not that I don't believe you, I really do and appreciated your help. Peace .

The reason why I so focused in gH number is I think it's easier for me to test both Ca and Mg with gH Test Kit only which I already have rather than focus on both Ca and Mg in ppm which I have to spend another $.24 for Ca Test Kit and $. 15 for Mg Test Kit.

So I though that it is easier and less work to do if I can target/add a certain degree of gH which have 4:1 of Ca and Mg at the beginning of the week and at WC time and suppose that the Ca and Mg that I add can provide enough nutrient for the plants in the whole week and I just test the Ca and Mg with gH Test Kit at the end of the week to see if it is used up or not or should add more. That's all. Thank you very much.


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## stevenlau (Jul 21, 2009)

I have just now try to add 4.5gr of CaCl2 and 3gr of MgSO4 that have already been dissolved into 1 liter of water before into my 80L tank (actual volume is 96L but minus substrate, wood, plants and plus filter volume, let's assume it's only 80L) and after 2-3 hours later I test the gH, it showed over 12dgH (until 12 times reagent drops, the color still show brown). What is wrong here pals? Please help. My water is 0-1dgH before I add those both CaCl2 and MgSO4.

What happens if there's too much Ca and Mg in planted tank? Should I immediately conduct water change?

I would like to make a stock solution of those Ca and Mg in 250ml bottle water. How do I count for 4:1 ratio of how much gr of Ca and Mg to add and 1ml of it will be how much ppm of Ca and Mg? Please, please help guys. 

Thank you very much.


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## Philosophos (Mar 1, 2009)

In reply to both your private message and above post,

1ppm CaCl2 = .9090ppm GH = .0509 dGH
1ppm MgSO4.7H20* = .2425ppm GH = .0136 dGH

*epsom salts, this is what you will be working with

Your tank is fine right now; somewhere around 3.7ppm Mg (a touch low) and dead on 20ppm of Ca.

Good luck overdosing Ca/Mg. You could dose 4x that and you'd have some people's tap water. Your soft water plants may not be happy, but a 75% WC would fix everything with the tap water you have. In short, most of us envy your ridiculously soft tap water 

For Ca/Mg, just work with EI and dosing; your Ca/Mg is unlikely to be higher than twice what you're dosing (still safe ranges) if you're doing EI. Some hard water plants can mess with things if you've got CaCO3 in the water, but you don't have enough to end up with that issue.

CaCl2 does not play nice with MgSO4 in my experience. Everyone says it should work fine; I end up with nasty precipitates no matter what method I use. Maybe it's forming CaSO4 or something.

For the MgSO4.7H2O solution, add 25.35g (or as close as you can measure to that) to half your volume of deionized water (125ml) then top up to 250ml. Stir for a while. Dose 1ml for every 2L of solution to get 5ppm Mg in your column.

For CaCl2 (odds are you have anhydrous, so there's no .nH2O to worry about. If it isn't, let me know) mix 27.69g the same way as above, dosed the same method, for 20ppm Ca.

In terms of testing for GH, you should make up a calibration solution. Mix up 5.44g of CaCl2 in 100ml of DI H2O. Every Ml you add to 1L of DI H2O will raise the water 1GH. If you test 2-3 GH in the column, test and see what 2-3 GH looks like on the calibration solution.

Careful with the CaCl2; wear gloves. It'll burn around your nails if you don't.

If you're feeling lazy at any time, you can pretty much just dose equal weights epsom salts to calcium chloride; 4.5g of each in 80L will get you 20ppm Ca, 5.46ppm Mg. You can also use the CaCl2 fert solution as a calibration solution; it should only be about 1.8% different in the results it gives.

For my own future reference on this thread, and maybe your own curiosity, here are the formulas I used to calculate things. They're MS Excel formated:

MgSO4.7H2O Solution:
=(246.47/24.30506*5)/(1000/250/2)

CaCl2 (Anhydrous) Solution:
=(110.98 /40.0784*20)/(1000/250/2)

GH Calibration Solution:
=(110.98 /40.0784*17.86*1.1)/(10)


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## johnzhou2476 (Nov 28, 2006)

Steve, where are you? Are you in New York? If so, you are very luck to have soft tap water. As for me, the target ca and mg level that I shoot for are 6ppm of Mg and 24ppm of Ca and 24ppm of K. For calcium, I use Calcium Sulfate. I've read that too much cacl2 is bad, because of too much chloride. I think Kekon had bad experience when Cl is over 5ppm. Also remember, harder water can take more Nitrate and Trace. So dose, N and trace accordingly to your GH.


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## johnzhou2476 (Nov 28, 2006)

Last thing I want to point out is that some plants prefer soft water and some prefer hard water. I find ca of 24ppm and mg of 6ppm to be a good middle ground. Also, the 4:1 ca to mg ratio is a general rule of thumb but does not apply for all plants. For example, ideal condition for Nessae is 2ppm of Mg and around 12ppm of Calcium. My Nesssae don't well under my current condtion, but everything else is fine.


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## johnzhou2476 (Nov 28, 2006)

Steve, use the fertilator and dose everything dry - it's really simple. I have a 110 gallon tank and I change 70 gallon of water every other week. I have zero GH and KH from my tap. Here's what I add to get everything to target level using Fertilator. 

70 gallon water change:
1/2 tsp of Potassium Nitrate
1/8 tsp of Mono Potassium Phoshpate
6 tsp of Equiliibrium
4 tsp of Calcium Sulfate
1 tsp of Calicum Choride
2 tsp of Magnesium Sulfate


Adding those will give me the following target for 70 gallon water volume:
Nitrate - 6ppm
Phoshpate - 1.5ppm
Calcium - 27ppm
Magnesium - 6ppm
Potassium - 28ppm


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## Philosophos (Mar 1, 2009)

I'm going to go on a bit of a rant here. It's definitely nothing personal, but I've got my opinions on dry dosing 

No fert measurement we use in the hobby is exact for any one plant. We don't have the funding to cover tests on a meaningful number of what the rest of the world calls weeds. Dosing consistently is important though; knowing that you've got 10ppm instead of 6-8ppm is important when you're watching your plants. These numbers are especially valuable when you know what happens at certain nutrient levels, but not why. This sort of thing becomes even more important when you're messing with things like emersed growth and misting nutrient solutions; some leaves wither easier than others.

Dry dosing isn't exactly simple; you have to premix everything every time you want to dose it, and measure out each compound. Just lumping in CaCl2 is a nasty thing to do to your fish, and CaSO4 has low solubility so those two are especially important. A couple of the K+ based ferts actually pull endothermic reactions that chill the water as well; I'm not sure the fauna wants to hang around for that either. On top of it all, your column nutrient distribution suffers if you haven't dissolved everything. Your measurements are also much more inaccurate and kind of wasteful if you're just dosing excess to make sure that you aren't under dosing for lack of accurate measurement.

By comparison, I mix up my batches every month or two, and it takes maybe a couple of hours because I like accurate measurements and sterility. From there, dosing consists of adding 20ml of one solution or the other; 5 seconds to dose with superior accuracy. Compare that to 5 minutes, 2.5 hours a month; already more than I spend mixing my solutions.

Now on top of that, using fertilator is using someone elses math and measurements. Have you bothered to check their density measurements or how they are arrived at? Have you read the old poling threads that simply averaged everyone's measurement of a random kitchen teaspoon as weight? Fertilator's actual math has improved to be pretty good (used to have nasty snags), but its volume presuppositions are rather messed up.

Why discourage someone who's looking for stock solution convenience and accuracy? Why not learn how to do it, and make it easier for others? The whole hobby can benefit from this. Most of this is perhaps grade 8-10 math, and maybe the first semester of grade 12 chemistry to be able to calculate your own solutions. If someone else does the math for you and writes instructions, then it's no more difficult than baking using a scale. The extra cost for this accuracy is about $40 for a pocket scale and a nice little graduated cylinder to dose with, and about 25 cents for the DI H2O.

This is not to say that dry dosing doesn't work. It does, and I won't doubt that. My issue is that it does not make better planted tank keepers. At that, even if it's dry dosed, I would recommend using fertilator (or any other fert calculator) only to double check your own math when custom dosing. If you can't see the formulas that they're using, you won't know if the numbers you're being given are accurate. I encourage people to double check my math for that matter; some have learned how, and now they're teaching others.


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## nfrank (Jan 29, 2005)

I personally measure all my dry chemicals using 1/4, 1/2 and 1 teaspoon measures. This is certainly more than sufficient for gypsum(hydrated CaSO4) and Epsom Salt (hydrated MgSO4), as well as the macros. Checking dosing amounts with the fertilator is a very good idea. 

Due to solubility issues mentioned and for other reasons, i dont add the dry chem directly to the tank. It only takes a few seconds more to dump them in a plastic bottle and shake it up to help get them dissolved . I use an old plastic Gater-ade bottle (I think it is 20oz (0.6L), maybe a little larger). Then i pour it in. I have also used this same approach for powdered dolomitic lime. Some of the chemicals are slow to dissolve so there can be a temporary suspension. 

I have been doing this for well over 10 years. 

Currenly, i have a sump and so, i now pour the suspension there and there are virually no small undissolved particles in the main tank.


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## wet (Nov 24, 2008)

Respectfully, I think you may be overstating the need for percise measurement as well as importance of dry vs solution dosing, Philosophos. The important thing is we keep putting fertilizers in the tank.

Let's say Sally has a tank such that 1/16th tsp KNO3 adds 5ppm NO3. Let's say Sally also mixed a solution where 5mLs of it adds 5ppm NO3. Sally doses these on alternating days (dry MWF and solution TThSa) because she's weird like that. Sally premixes that dry dose in a cup before adding it to a tank when keeping stupid hungry fish and doses straight into the tank when not. Sally has cyano and thread so she's pretty sure she needs more N. So, she adjusts:

On dry days she pulls out her 1/32th tsp teaspoon and adds 3 levelled portions.
On wet days she pulls out the solution and adds 7.5mLs.
Either one is 7.5ppm NO3.

After a couple weeks of this she's beat Cyano but thread is still around.

On dry days she uses her 1/8th tsp to add a levelled portion.
On wet days she pulls out the solution and adds 10mLs.
Either one adds 10ppm NO3.

So why does it matter? If a person prefers dry, that's totally okay and can be scientific. The best method is the one that gets Sally (or Joe...) to keep his plants fed.

While K can cause an endothermic reaction, come on. It's 20ppm K into a huge volume... I'd claim more absolute impact from, say, my halogen table lamp I use when reading by the tank.  Your points make me think about the harshness of certain chemicals on my pets, though, and I will adjust.
Still, some of your points are good and I see where you're coming from, but fear it'll scare away those folks on the fence between buying dry fertilizers vs commercial fertilizers (or not dosing at all!). Any of these methods are just as valid.

Because it may help you understand this other point of view, let me add that I type this as a guy with nice nerd supplies (a nice Ohaus scale that does 10mg increments, a decent TI calculator, these things for dosing bottles, etc). 









And even with all of it, I still round to make my life easier. For example, when using solutions I prefer to mix with a target of 5mLs per dose, because measuring 5mLs is _easy_ (it's about a tablespoon, bottle cap, has a fat line on my syringe, etc). When I dose dry I use tiny teaspoons. In either case I realize I could get away with less precise equipment. I just happen to be wired to like this stuff. And you are, too. But a guy who knows plants can grow plants just as nice as either of us if he's got a good sense of fertilizers and a good eye for eyeballing doses. All that matters is we get this stuff in the tank when the plants need it.

<3


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## Philosophos (Mar 1, 2009)

wet said:


> Respectfully, I think you may be overstating the need for percise measurement as well as importance of dry vs solution dosing, Philosophos. The important thing is we keep putting fertilizers in the tank.


Why? I said dry dosing works, and people should use it if that's what they want to do. I did not say that dry dosing was necessary for a nice tank, but rather the next step in fine tuning. There are times when it pays to know your measurements, and usually educating yourself on how to mix fertilizers means you're looking more closely at what each nutrient does.



wet said:


> Let's say Sally has a tank such that 1/16th tsp KNO3 adds 5ppm NO3. Let's say Sally also mixed a solution where 5mLs of it adds 5ppm NO3. Sally doses these on alternating days (dry MWF and solution TThSa) because she's weird like that. Sally premixes that dry dose in a cup before adding it to a tank when keeping stupid hungry fish and doses straight into the tank when not. Sally has cyano and thread so she's pretty sure she needs more N. So, she adjusts:
> 
> On dry days she pulls out her 1/32th tsp teaspoon and adds 3 levelled portions.
> On wet days she pulls out the solution and adds 7.5mLs.
> ...


Nice example, but have you ever sat down and weighed the accuracy of teaspoons? I get about a +/-15% margin of error when it comes to weight. Opening and closing bags daily around a humid fish tank adds moisture; you could easily add 5-10% more weight that way long term. A +/-20 or 25% margin of error isn't always acceptable, especially if you're playing with nitrogen limitation.



wet said:


> So why does it matter? If a person prefers dry, that's totally okay and can be scientific. The best method is the one that gets Sally (or Joe...) to keep his plants fed.


I agree; consistent feeding comes first. I do not think that dry dosing will ever be as accurate as working from stock solution though, and dry dosing does not meet the needs of all aquarists. Planted tank keepers who want to keep it simple always will; we even make methods that cater to people who are very specifically not interested in spending time with their tanks. At the same time, I would certainly NEVER discourage someone who wants to learn the next level of keeping their tank.



wet said:


> While K can cause an endothermic reaction, come on. It's 20ppm K into a huge volume... I'd claim more absolute impact from, say, my halogen table lamp I use when reading by the tank.  Your points make me think about the harshness of certain chemicals on my pets, though, and I will adjust.


My concern isn't an even distribution, otherwise I'd say to wait an hour after premixing. My major concern is just dumping things directly into the tank with localized clumps. After all, we don't count the entire mass of all food in the room if only one drumstick has dangerous concentrations of salmonella. I won't say I know how dangerous the K+ is, but my experience with CaCl2 encourages me to err on the side of caution.



wet said:


> Still, some of your points are good and I see where you're coming from, but fear it'll scare away those folks on the fence between buying dry fertilizers vs commercial fertilizers (or not dosing at all!). Any of these methods are just as valid.


Any of the methods work, dry is cheaper than commercial and you'll end up with better dosing because you can afford to dose regularly. Even purchased solids are commercial fertilizers though; they're just cheaper. Right now there's no reasonably priced liquid outside of perhaps bulk pfertz given production costs.



wet said:


> Because it may help you understand this other point of view, let me add that I type this as a guy with nice nerd supplies (a nice Ohaus scale that does 10mg increments, a decent TI calculator, these things for dosing bottles, etc).


I'm not much for ad hominems; for better or worse 



wet said:


> And even with all of it, I still round to make my life easier. For example, when using solutions I prefer to mix with a target of 5mLs per dose, because measuring 5mLs is _easy_ (it's about a tablespoon, bottle cap, has a fat line on my syringe, etc). When I dose dry I use tiny teaspoons. In either case I realize I could get away with less precise equipment. I just happen to be wired to like this stuff. And you are, too.


Actually I figured out that I save myself about an hour a month wet dosing using a small graduated cylinder rather than waiting for compounds to dissolve, and I dose precisely rather than guessing.



wet said:


> But a guy who knows plants can grow plants just as nice as either of us if he's got a good sense of fertilizers and a good eye for eyeballing doses. All that matters is we get this stuff in the tank when the plants need it.


You can grow nice plants, yes. But if you want to push out reds through N limitation, figure out GSA equilibrium for PO4 to any accuracy, or save yourself about 15-25% on your dry fert consumption, then you'd want to do liquid.

I'd really like to know where you got the idea that I'm against dry dosing given that I clearly stated I wasn't:


Philosophos said:


> This is not to say that dry dosing doesn't work. It does, and I won't doubt that.


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## stevenlau (Jul 21, 2009)

johnzhou2476 said:


> Steve, where are you? Are you in New York? If so, you are very luck to have soft tap water. As for me, the target ca and mg level that I shoot for are 6ppm of Mg and 24ppm of Ca and 24ppm of K. For calcium, I use Calcium Sulfate. I've read that too much cacl2 is bad, because of too much chloride. I think Kekon had bad experience when Cl is over 5ppm. Also remember, harder water can take more Nitrate and Trace. So dose, N and trace accordingly to your GH.


Thank you johnzhou2476, I'm from Indonesia and no, I still don't have tap water supplied yet instead I or we use ground water for our others need. I buy RO water from my local water supplier depot for drinking water and also for my tank's water  and it costs around $. 1 per 38 liters.

Btw, what is the disadvantage of having high Cl in our planted tank?


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## stevenlau (Jul 21, 2009)

Philosophos said:


> 1ppm CaCl2 = .9090ppm GH = .0509 dGH
> 1ppm MgSO4.7H20* = .2425ppm GH = .0136 dGH


Thank you so much Dan . According to APC Fertilator when I dose 4.5gr CaCl2 and 3gr MgSO4 in 80liters, I would have 20.31ppm CaCl2 and 3.7ppm MgSO4 and referring to your formula above I should have barely 1.08dgH increase but why when I test the gH, it reads over 12dgH. My gH was 0-1dgH before dosing those CaCl2 and MgSO4.



Philosophos said:


> CaCl2 does not play nice with MgSO4 in my experience. Everyone says it should work fine; I end up with nasty precipitates no matter what method I use. Maybe it's forming CaSO4 or something.


Yes, me too, it was precipitated. Now I make myself a stock solution of those two separetely.



Philosophos said:


> For CaCl2 (odds are you have anhydrous, so there's no .nH2O to worry about. If it isn't, let me know)


I really have no idea at all if I have CaCl2 in anhydrous or dehydrated or anything else as I don't know for sure what are those terms exactly  anyway, here's the pic of my CaCl2 I bought and the shopkeeper told me it's food grade.











Philosophos said:


> Careful with the CaCl2; wear gloves. It'll burn around your nails if you don't.


Thank you . I can feel the water becomes hot when I stir it.

One more last thing about dosing target, say if I target 2.0ppm PO4, should I divided it by 3 which is 0.66ppm every time I dose for 3x in a week or 2.0ppm every time and result in 6.0ppm in a week?

Thank you so much.


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## Philosophos (Mar 1, 2009)

stevenlau said:


> Thank you so much Dan . According to APC Fertilator when I dose 4.5gr CaCl2 and 3gr MgSO4 in 80liters, I would have 20.31ppm CaCl2 and 3.7ppm MgSO4 and referring to your formula above I should have barely 1.08dgH increase but why when I test the gH, it reads over 12dgH. My gH was 0-1dgH before dosing those CaCl2 and MgSO4.


Ya, that's how it should've gone. Mix yourself up a bottle of CaCl2 as per instructions, drop 1ml of it into 1L RO water and check your results. You should get 2-3 GH off of it. If you don't, the test kit has spoiled some how.



stevenlau said:


> I really have no idea at all if I have CaCl2 in anhydrous or dehydrated or anything else as I don't know for sure what are those terms exactly  anyway, here's the pic of my CaCl2 I bought and the shopkeeper told me it's food grade.


Anhydrous means it doesn't have water bound to it. Something like Calcium Chloride monohydrate would be CaCl2.H2O rather than just CaCl2.

Yours looks like anhydrous, though the reflective parts shouldn't be there. It should be dull all over. Ask to see the packaging perhaps?



stevenlau said:


> One more last thing about dosing target, say if I target 2.0ppm PO4, should I divided it by 3 which is 0.66ppm every time I dose for 3x in a week or 2.0ppm every time and result in 6.0ppm in a week?


Yes, divide by 3. Dosing 6ppm is useful if you've got a GSA problem, but I find myself without deficiency dosing a little over 2ppm because of phosphate from feeding.


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## wet (Nov 24, 2008)

Philosophous,


> But if you want to push out reds through N limitation, figure out GSA equilibrium for PO4 to any accuracy, or save yourself about 15-25% on your dry fert consumption, then you'd want to do liquid.


Not true. One can limit N dry or via solution. One can adjust and know input P with or without solution. And I think all your claims about dry dosing being inaccurate assumes someone is using a poor method. I could just as easily point out that using solutions uses more equipment and more steps, increasing the chances for cross contamination and error.



> I'd really like to know where you got the idea that I'm against dry dosing given that I clearly stated I wasn't:
> 
> 
> Philosophos said:
> ...


... um, your sentence you omitted.


> My issue is that it does not make better planted tank keepers.


My whole point is either one is as good as the other. One is not better.



> I'm not much for ad hominems; for better or worse


I really am sorry if you took my saying "nerd supplies" is some personal attack on you. It was a joke meant to make you laugh after your statements of precision and accuracy.


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## Philosophos (Mar 1, 2009)

wet said:


> Not true. One can limit N dry or via solution. One can adjust and know input P with or without solution.


But not to the same accuracy. You can try to limit it and play "watch the plant" but this is much like those who say drop checkers are useless because they can watch what happens over 2 days, where I can tell in 2 hours once I'm familiar with the flow dynamics of a tank. It's impossible to say that with the same set of known variables extended by any amount that the knowledge of the subject will be less. I will prove this next.

And I think all your claims about dry dosing being inaccurate assumes someone is using a poor method. I could just as easily point out that using solutions uses more equipment and more steps, increasing the chances for cross contamination and error. [/quote]

You'd probably be alone on the assertion that a stock solution is as inaccurate as dry dosing by volume.

To be fair, lets say the average person has a palm scale accurate to +/-.1 of a gram. When I mix up a stock solution, I make 3 measurements; 2 of about 60g, 1 of about 6g. That's +/-.3g in 126g, or about +/- .002380%. I make 2 liquid measurements; the initial measurement and the top-off. We'll say I'm inaccurate from there, and that my topoff is 10ml inaccurate for a further +/-1%. We'll call another ml or two if you like for what drips off the stir stick that isn't in perfect solution, bringing the total points of inaccuracy unique to my method up to +/-1.102380%.

Now speaking on humidity, the average person would need to open their bags between 7 and 70 times for 1L macro solutions for EI dosing depending on the compound. Dry dosing depends on aquarium volume, but for a 20 gal dosing 1/8 tsp of KNO3 at a time, the number looks like 7000 times. What sort of levels of humidity is that going to add? Are you really going to take the time to use dessicants in the bag? Double up containers? Store it in a dry wooden cupboard that seals well? I've got little doubt that my storage method leaves things around 0% RH, and at least 1/100th the exposure to whatever the air happens to be; probably around 30-50%. At 13mg/L H2O in the air (40% RH at 20c) with (lets conservatively say) 200ml of air displaced with every bag opening, 7000 times, the bag ends up being resealed in total with 53mg of H2O per gram presuming the bag always contains 1lb of fertilizer... twice that if the median (~226g) is used. Compare at most the 1% level of exposure for my method. Liquid methods max out at 2-4% humidity gain possible, dry dose at 18-36%. I say 20% moisture increase for dry dosing because it fits with practical storage numbers for better known household items getting the same treatment like salt and flour.

Next lets look at dry dose volumetric measuring. This one is kind of left to individual tests, but I've never been able to measure to more than +/-5% when I trained myself to measure by volume accurately using teaspoons. When I stopped checking myself with a scale, that number went to more like +/-15%, and clumps from moisture really threw things off. I would invite anyone here to try the same and test their results. Even if we claim 5% accuracy in weight from volumetric measurement and add it to humidity, dry dosing has about a +/-25% margin of error vs. about 5% for liquid.

Now, just for bonus points, I mix up 6 1L bottles at a time, so most of my bags are opened no more than twice in their lifetime meaning humidity is relegated to the supplier's storage and shipping. At worst a bag gets opened 9 times for things like KH2PO4. For the sake of argument, we'll say I open a bag 3x for a max exposure of .17mg/g H2O, or about 0.00017% (+/-0.000085%) maximum possible deviance. On top of that, even though I use a better scale (.03/g) the average person could do a 6 batch mix and end up with even less of an infinitecimal level of deviance.

There are other things, like residue on spoons and supplier storage conditions, but any of these (as near as I can tell) are matters that effect both methods. Unless you can prove the margin of error introduced by them makes efforts at more accurate measurements negligable, I can't see why dry dosing by volume would be more accurate.



wet said:


> I really am sorry if you took my saying "nerd supplies" is some personal attack on you. It was a joke meant to make you laugh after your statements of precision and accuracy.


No, it's not that. I made the statement more for the fact that I couldn't tell if you meant that knowledge of science has little to do with competency in dosing, or if your credentials were supposed to influence the prominence of what you were saying. This is why I said "for better or worse" because of course the inverse of ad verecundium would be ad authoritatem.


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## stevenlau (Jul 21, 2009)

Philosophos said:


> Ya, that's how it should've gone. Mix yourself up a bottle of CaCl2 as per instructions, drop 1ml of it into 1L RO water and check your results. You should get 2-3 GH off of it. If you don't, the test kit has spoiled some how.


Indeed I have just try to calibrated it and appears that it's quite accurate. I drop 3ml of "mixed 5.44gr CaCl2 in 100ml RO" into 1L RO and the result was 8dgH.



Philosophos said:


> Yours looks like anhydrous, though the reflective parts shouldn't be there. It should be dull all over. Ask to see the packaging perhaps?


That's is not the reflective cause by camera shot, it's really there, so in this case I guess I got the monohydrate? I think there's water in it for it's kind of feel sticky (image that your hand is wet when touching that powder) and I just got the plain white plastic bag when purchasing it .

Thank you.


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## wet (Nov 24, 2008)

stevenlau,

A thing to add to one of your earlier questions is that plants can suffer from Cl toxicity and you'll find pictures around documenting it. FWIW I have not seen it and used to dose KCl and CaCl.

Philosophos,



> wet said:
> 
> 
> > I really am sorry if you took my saying "nerd supplies" is some personal attack on you. It was a joke meant to make you laugh after your statements of precision and accuracy.
> ...


Dude, I was saying I use precise liquid dosing, too. Maybe I'm misreading this to think you're suggesting I was trying to show you up or compare credentials or some junk, so just to be clear, let me state my credentials:

1) I really like plants.
2) I like reading from and contributing to the best aquatic plant site on the Internet.
3) I post pics of my tanks and plants so people get a reference point for my opinions.
4) I like reading other people's opinions.

And that's it. In other words, I'm just like most of the fellas and ladies on APC. No better or worse.



> To be fair, lets say the average person has a palm scale accurate to +/-.1 of a gram. When I mix up a stock solution, I make 3 measurements; 2 of about 60g, 1 of about 6g. That's +/-.3g in 126g, or about +/- .002380%. I make 2 liquid measurements; the initial measurement and the top-off. We'll say I'm inaccurate from there, and that my topoff is 10ml inaccurate for a further +/-1%. We'll call another ml or two if you like for what drips off the stir stick that isn't in perfect solution, bringing the total points of inaccuracy unique to my method up to +/-1.102380%.


1) it's 0.238%, not .002380%.
2) The guy fast with the scale stops at the .002380g/1g number and leaves out that error with the dosing container.



> Now speaking on humidity, the average person would need to open their bags between 7 and 70 times for 1L macro solutions for EI dosing depending on the compound. Dry dosing depends on aquarium volume, but for a 20 gal dosing 1/8 tsp of KNO3 at a time, the number looks like 7000 times. What sort of levels of humidity is that going to add? Are you really going to take the time to use dessicants in the bag? Double up containers? Store it in a dry wooden cupboard that seals well? I've got little doubt that my storage method leaves things around 0% RH, and at least 1/100th the exposure to whatever the air happens to be; probably around 30-50%. At 13mg/L H2O in the air (40% RH at 20c) with (lets conservatively say) 200ml of air displaced with every bag opening, 7000 times, the bag ends up being resealed in total with 53mg of H2O per gram presuming the bag always contains 1lb of fertilizer... twice that if the median (~226g) is used.


This is exactly what I mean about making the assumption of bad method by dry dosers. You realize that, using your assumptions for this calculation, that 7000 doses is almost 20 years of religious daily dosing? Who does that?

Let's say (using your math, rounded to the nearest mg) that my friend Sally:

1) Measures out enough of whatever substance to dose 350 times, or one year, and puts it it some easily accessible air tight spice jar.

2) She then puts the 1lb bag with the bulk of the fertilizer in the same place you store your 1lb bag between making solutions.

3) She would have ~2.5mG per gram affected by humidity. In other words, 0.25 % percent error. Less than any of our scales.

I think we've reached the point of semantics when we're debating percent error in calculations that are much smaller than the margin of error in even the nicest equipment. But please feel free to have the last word if you would like it


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## stevenlau (Jul 21, 2009)

Thank you wet for your Cl toxicity and please both of you (philosophos) stop debating. I see the point from both of you, dry is fine and so as premix solution. Many peoples like direct dry but so many people like premix too like myself. Just let the others figure out themself, ok? Peace


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## nfrank (Jan 29, 2005)

I agree with Stevenlau. Lets keep the tone civil, or you will loose folks including me from the conversation.



> From "Wet". A thing to add to one of your earlier questions is that plants can suffer from Cl toxicity and you'll find pictures around documenting it. FWIW I have not seen it and used to dose KCl and CaCl.


I think it is worth talking about this point a little. CaCl is very soluble and so is so much nicer than gypsum or dolomite for dosing. If Cl is really not a concern, that would be good. I have stayed away from it to avoid Cl buildup, but like wet says, that may be an unnecessary worry.

The version i have used in the past is the one in ice melt or desiccants (nice product called Damp Rid). I believe this is the anyhydrous CaCl2 which means no water attached to the CaCL2 molecule. It is not a powder but comes as prills. VERY cheap in home depot or lowes. However, it quickly soaks up water which affects the wt per tsp, but i am not sure that there is much change in the volume. Until it gets very sticky, it can probably be reliably dosed using "dry" measures (tsp, Tbs). It can also be restored to true dry condition by baking. DampRid is very nice product BTW to use in closets adjacent to a fish room.

I have never seen or used the specific forms, like "monohydrate" which only has one H2O attached or dyhydrate with 2 waters, when they are in their dry form. I am not familiar with their affinity for soaking up more water compared to the common type, nor how expensive to purchase. Is it really worth getting? Regarding purity, some grades have slightly less contaminants like very small % of NaCl. Also a non issue for me. The product is also availabe as flakes. Do they have less moisure when packaged? Also, what "form" is sold by our favorite fert supplier? IMO, the dryness of CaCl2 and how it is stored (glass container or zip lock or thick freezer bag) are important, especially to do the initial fertilator conversion of milligrams (mg) to tsp. Just keep it from getting sticky and I think you should be OK for subsequent dosing.


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## Philosophos (Mar 1, 2009)

Steve, sorry about the threadjacking. I'll delete the text wall I had typed and give peace a chance 

Ok, a little wetness would account for things. Odds are its anhydrous; your calibration solution would've given much different (lower ppm) results otherwise.

Now what's going on in your tank is beyond me. Something must be leeching out or sneaking in. Could you test your KH for us? Are there any rocks in the tank?

nfrank, Cl2 is a common question with CaCl2. I thought it should've been toxic at one time, but experience shows otherwise. Either way, it's not a bad idea to revisit.

CaCl2 is 70.906/110.98 g/mol Cl and 40.074/110.98 g/mol Ca.

To get 20ppm Ca in 1L of pure H2:

=110.98/40.074*20
=55.38753306383191

Or about 55.4mg of CaCl2.

This contains a certain amount of Cl2 of course, which is figured out with this equation:

=55.4*70.906/110.98
=35.39549828797982

Or about 35.4ppm Cl. I'm guessing given its reaction to water and the fumes it gives off, the Cl2 isn't hanging around very long; the levels of Cl2 in the solution may drop rapidly.

The EPA max sits at 250ppm. Right now I don't have an hour or two to sort through the ecotox database, but if anyone would like to do the homework then here's a great site for toxicity:
http://cfpub.epa.gov/ecotox/quick_query.htm

Enter 7782-50-5 under the chemical entry for chlorine. From there query aquatic, and look for plants/fish that relate to our hobby. Cold water fish and daphnia tend to be sensitive, so they aren't great examples for toxicity when dealing with tropical fish and plants.


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## Minsc (May 7, 2006)

stevenlau said:


> I have just now try to add 4.5gr of CaCl2 and 3gr of MgSO4 that have already been dissolved into 1 liter of water before into my 80L tank (actual volume is 96L but minus substrate, wood, plants and plus filter volume, let's assume it's only 80L) and after 2-3 hours later I test the gH, it showed over 12dgH (until 12 times reagent drops, the color still show brown). What is wrong here pals? Please help. My water is 0-1dgH before I add those both CaCl2 and MgSO4.
> 
> What happens if there's too much Ca and Mg in planted tank? Should I immediately conduct water change?
> 
> ...


I am curious if there is some reaction that could be throwing off the test kit? I have a similar situation in that I added 3 tsp CaCl and 1.5 tsp MgSO4 to my 45 gallon tank, as my tap has almost no hardness at all. Now my test kit says I have over 20 dGH! The liquid never turned from orange to green, at some point I just gave up. The test kit normally seems very reliable, I'm sure something is affecting the reading.


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## stevenlau (Jul 21, 2009)

Philosophos said:


> Steve, sorry about the threadjacking. I'll delete the text wall I had typed and give peace a chance
> 
> Ok, a little wetness would account for things. Odds are its anhydrous; your calibration solution would've given much different (lower ppm) results otherwise.
> 
> Now what's going on in your tank is beyond me. Something must be leeching out or sneaking in. Could you test your KH for us? Are there any rocks in the tank?


It's alright 

Anyway my kH is 0-1 dkH and there are some rocks but they are petrified wood rocks. I just bought Sera Calcium Test Kit and have tested in my tank, the result is around 30-40ppm of calcium and right now my gH is at 4 dgH (after overdosed earlier, I did 50% wc).

What is so difficult to measure the calcium using Sera Test Kit is each reagent drop of it will represent a 20ppm of Ca and after the second drop the color turned to blue which indicate I have around 30-40ppm of Ca. How can I make that Test Kit measures a little finer?

The product consists of 2 liquid reagents and 1 powder reagent. The instruction is fill 5ml of aquarium water to the test vial and add 8 drops of reagent 1 and then add a level-filled spoon of reagent 2 (powder) lastly add reagent 3 drop by drop (each drop indicates 20ppm calcium) until the color turns from pink via violet into blue. The question is suppose I fill 5ml of aquarium water + 5ml of distilled water and doing the rest same as above, should each drop of reagent 3 represents 10ppm of Ca instead of 20ppm? How about making the test kit to be able to measures even finer of 5ppm Ca each drop?

Thank you once again in advance.


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## Philosophos (Mar 1, 2009)

Good idea, but I think you'd just double the sample size rather than diluting with RO.

You may also need to increase the amount of reagent you're using to start.

It should work one way or the other in principle though. I know for GH/KH tests it's possible to simply double the quantity of sample size to get half the resolution per drop. Given that you now have a calibration solution it's possible for you to test multiple methods to see what works.


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## adrideh (Jun 26, 2008)

Hi, so sorry if my question sounds dumb, as I am netiher a highly educated scholar nor have a vast experience of planted tanks.

I've been very very interested in this discussion, and have a little question.

Some people say we can measure GH from using a TDS meter, and divide the result shown by 20 (this number is rather confusing for me as some say 18 some say 21). Is this correct ?

If so, doesn't TDS meter measure the total conductivity in a water source ? Meaning it may not always be Ca / Mg ?

Thanks in advance....


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## johnzhou2476 (Nov 28, 2006)

Hey guys, I've been doing a lot of pondering and researching on Ca and Mg lately. I've tried different ca;mg ratios, including ideal 4:1 ratio that a lot of folks are talking about. But, yesterday I found a posting by Edward and both Tom Barr and him basically agree that there's no real evidence to support such ratio. Edwards says, for calcium all you need is to have around 20-30ppm at water change and about 2ppm for magnesium. Edward further says that calcium is an immobile nutrient and that all you need to do it to set and forget it. But as for Magnesium, it's a mobile nutrient and that you would need to dose it a little bit everyday, maybe like .2ppm daily. Furthermore, high mg level, like 10ppm is bad for certain plants such as Nesea and Rotala Wallicii. What got me even more confused was that posting from an individual who had hard water with ideal ca;mg ratio but still experiencing stunting/leaf curling and co2 level was good, but after adding little mg, plants recovered and became less pale. So, you can say I'm kinda confused. My ultimate goal is to find that holy grail water parameter where all plant specimen would grow well. BTW, for all the hard core folks out there, why can't we all just use RO/DI water? This way it's somewhat standardized and we can all compare notes.


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## johnzhou2476 (Nov 28, 2006)

Not exactly. GH measures your Ca and mg ion. TDS is measuring your total dissolved solid, which could be other things like potassium, chloride, nitrate, organic waste, etc... you get the idea. TDS will give you a general idea. For example, my NYC tap water is super soft with TDS reading of 37ppm. I have near zero GH and KH which correlates to the low TDS reading.


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