# Using RO water only in cardinal tetra/Cory habrosus tank



## jschall (Apr 13, 2009)

I'm running a 10g tank with all RO water (purchased from LFS), with corydoras habrosus and cardinal tetras. I intend to go pressurized CO2 and high light. I don't want to use any tap water. I'm dosing 1/64 tsp CSM+b, 1/16 tsp kno3, and 1/64 tsp kh2po4 3x/week and changing 50%/week.
Do I need to add anything like seachem equilibrium or seachem fresh trace? Do I need to raise KH before doing pressurized CO2?


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## TLe041 (Mar 20, 2010)

Is there anything particularly wrong with your tap water? 

The two fishes that you're planning on keeping aren't overly sensitive, so using purchased RO water is an added expense that you can skip.


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## jschall (Apr 13, 2009)

TLe041 said:


> Is there anything particularly wrong with your tap water?
> 
> The two fishes that you're planning on keeping aren't overly sensitive, so using purchased RO water is an added expense that you can skip.


Water here is very hard. Don't want to have to use conditioner, and cost of RO is negligible for a 10 gallon tank.
Mainly I just want to know if I need KH to do CO2 with soft water fish, and if so, what's the best way to increase it and keep it stable?


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## onefang (Apr 10, 2011)

Your pH may drop considerably if you don't have at least 1 dKh. There are a variety of ways to get it(most will probably involve experimentation). Equilibrium is primarily for raising GH not kH.
Seachem does sell a product for maintaining kH called "Alkaline Buffer". I am not entirely sure of it's effectiveness, as I haven't ever used it. 
I have experimented with sodium bicarbonate(baking soda) to raise kH, and it works, but you will have to experiment with it to get your desired kH, without majorly raising the pH.

Here is a calc for how much baking soda to add, if you want to go that route:
http://www.dataguru.org/misc/aquarium/calKH.asp

Another method for modifying kH, is adding a small bag of crushed coral to your filter. For a 10 gallon, I wouldn't think you'd need more than a half cup or so to get decent kH, without spiking your pH too much.


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## Tex Gal (Nov 1, 2007)

Why not try going half and half? Do half tap water and half R/O. I've done this with my shrimp tank and plants and critters to great. I don't have to worry about reconstituting.


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## bosmahe1 (May 14, 2005)

Tex Gal said:


> Why not try going half and half? Do half tap water and half R/O. I've done this with my shrimp tank and plants and critters to great. I don't have to worry about reconstituting.


+1 on this suggestion.


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## onefang (Apr 10, 2011)

Mixing half and half would still require that you use water conditioner though, or let your tap water age in a bucket before you use it. Even then, you still may be introducing heavy metals(however unlikely that may be).


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## kamel_007 (Jan 7, 2006)

take it simply, i have sensitive fish in my 53g tank, i use ro water and mix it a little bit with tap water, instead of playing in water chemistry and buffering methods, my tap water is very hard here, anyway u can use declorenator or let the tap water ariated 24 hours before adding it,


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## jschall (Apr 13, 2009)

I'd rather cut the tap out entirely, because it represents variables that can't be compensated for unless I get a report on what's in it.


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## onefang (Apr 10, 2011)

Crushed coral is going to be your best bet for more consistent kH and pH levels. If I recall, the baking soda method tends to need constant attention, where as the crushed coral dissolves at a fairly steady rate keeping things pretty stable.


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## jschall (Apr 13, 2009)

onefang said:


> Crushed coral is going to be your best bet for more consistent kH and pH levels. If I recall, the baking soda method tends to need constant attention, where as the crushed coral dissolves at a fairly steady rate keeping things pretty stable.


But are either necessary?


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## onefang (Apr 10, 2011)

jschall said:


> But are either necessary?


Basically, if you don't have at least one dkh, your ph is going to get really low when injecting CO2. It's really up to you, your fish might tolerate the acidity. I am assuming that your pH is somewhere around 6 or lower if you are using pure RO(this is also assuming there isn't anything else in the tank acting as a buffer). When you add CO2 into the mix, your pH is only going to get lower. You can try it, but I'd def. recommend having at least 1 dkh for stability's sake(which a small bag of crushed coral should give you pretty easily).


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## kamel_007 (Jan 7, 2006)

i used crushed corals it raised my PH, the best thing is to keep ur water balanced.


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## onefang (Apr 10, 2011)

Due to the kH/pH relationship, you'll see a corresponding rise in pH, dependent on how much your kH has risen(this is assuming that there aren't any other buffering agents in the tank). I am not entirely sure what keeping your water balanced means though.



kamel_007 said:


> i used crushed corals it raised my PH, the best thing is to keep ur water balanced.


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## jschall (Apr 13, 2009)

Well, I've been injecting 1 bps co2 into this 10 gallon tank with a pretty high-efficiency reactor for a little over a day now, including overnight (didn't turn it off.) Cardinal tetras are happy. Cories are happy.
Only concern is running into calcium deficiency for the plants. The light came, and is on the tank now.


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## timwag2001 (Apr 15, 2009)

dont use crushed coral if you are using a ph monitor. i experienced what was described to me as a death spiral. the co2 lowered the ph, the cc raised the ph so the monitor would turn back on which lowered the ph, the cc dissolved and raised the ph which turned on the co2, which killed my fish


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## onefang (Apr 10, 2011)

Wow. I hadn't considered that. That's like the perfect aquarium storm.


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## kamel_007 (Jan 7, 2006)

i mean to get kh stabe at 5 and and ph at 6.5 for instance,
then keep up with that parameters
i have used that way


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## lanceduffy (Jul 15, 2010)

> Water here is very hard.


How hard? GH and KH please.


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## apistomaster (May 24, 2008)

lanceduffy said:


> How hard? GH and KH please.


These really are the questions that must be answered in order to give any useful advice.
But there are some other issues. I'm all for using the best water chemistry for the fauna and flora you want to keep but you seem to have placed some magical value on RO water yet want to alter it. You seem unrealistically averse to using any chlorine/chloramine neutralizer(water conditioner)
If you do not have test kits you can't know what your water chemistry is at any given time. 
At the very least, request a full test report from your water utility. It is free and very comprehensive.
I have been breeding my own Corydoras habrosus for many years and they are more productive in soft water than they are in my tap water. My tap water has a pH of 7.4, KH 6*, GH 6* and the TDS is 240 ppm.
Since the KH and GH are so similar that is what some of us would consider to be "balanced".
I use 25% tap water and 75% RO water for breeding C. habrosus.
At this ratio no water conditioner is necessary to neutralize chlorine/chloramine but I do use a few drops of SeaChem's Prime to neutralize the disinfecting chemicals added by the water utility. You never know when an extra dose has been used upstream from you either at the plant or after line repairs.
The final pH is about 7.0 and KH and GH both run 2 or 3 degrees. This is enough to prevent any abrupt pH crashes. No other chemicals are necessary since the portion of tap water I use adds all the minerals and at the right proportions.

There is no rational for forcing the fish you say you are keeping to live in "neat" RO water. This is unsafe for so many reasons.
1. The cells of the fish will want to expand and burst due to higher internal cellular osmotic pressure without a countervailing osmotic pressure from dissolved minerals in RO water.
2. It is very difficult to maintain a constant pH that is not to acid.
3. The use of CO2 in only RO water exacerbates points #1 and #2.


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## jschall (Apr 13, 2009)

I started using 1 part tap, 3 parts RO, because of plant deficiencies. I thought RO would eliminate variables, but because the normal trace mixes (csm+b) are not sufficient, I ended up doing this. I'm also dosing equal parts mgso4 with my csm+b now.

I just dose enough water conditioner to treat the amount of tap water I've added, per the label, plus a little extra.


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## aquaphish (Jan 22, 2005)

I use only RO water in all my tanks and my kH has been running at around 4-6dkH for years. 

What I add when making weekly water changes are the regular micros/macros-CSM+B, KNO3, K2SO4, KH2PO4 and nothing else. I do have ADA Amazonia I in one setup and Eco-Complete in another. Filtration is just a sponge and ceramic type media.

Test your kH weekly and determine for yourself if you need to add any form of stabalizer for kH. If you do then add 1 part of tap water to 3 parts RO. Test after several hours and see if your kH is within the spectrum you want. Increase the amount of tap water until you get the results you need. But to be honest I have not had to add any tap water to set my kH.

Also instead of using dry ferts, which is not the best to do when dosing small tanks, mix yourself some fert solutions per the Fertilator. When using dry in small setups you can miss the "mark" by not dosing quite enough or dose too much. By using ferts in solution you will get a more precise measurement and are able to better control your dosing. With a little experience using solutions you will be able to dose smaller and more precise amounts if needed to set your target, which you can not do by dosing 1/64 of a tsp. How would you add only say 10% of a 1/64tsp of dry ferts?


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## timwag2001 (Apr 15, 2009)

why would you want to add 10% of 1/64tsp?


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## onefang (Apr 10, 2011)

aquaphish said:


> I use only RO water in all my tanks and my kH has been running at around 4-6dkH for years.
> 
> What I add when making weekly water changes are the regular micros/macros-CSM+B, KNO3, K2SO4, KH2PO4 and nothing else. I do have ADA Amazonia I in one setup and Eco-Complete in another. Filtration is just a sponge and ceramic type media.
> 
> ...


If you are at 4-6dkH running pure RO, then one of two things is happening.
You have something in your tank that is breaking down under the acidity of the RO, adding to the carbonate hardness(Which shouldn't happen if you are running AS, or decently aged EC).
Or, you really really need to replace your RO membranes.
RO should be totally bare, IE, no kH, no GH, generally a pH around 6(or lower), and a TDS of 0 on decent membranes.



> why would you want to add 10% of 1/64tsp?


LOL!


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## aquaphish (Jan 22, 2005)

timwag2001 said:


> why would you want to add 10% of 1/64tsp?


The question is not why but how would you add such a small amount. I am just attempting to show that dry vs. solution you have a better control to adjust your fert levels.

With a solution you can add just half a mil of solution if you needed. I have a 1 gal betta tank. When I am adding a solution of CSM+B which is a mix of 6g. of dry CSM+B added to 125mils of RO water to get a target of .15ppm Fe I need to add only .25mils of the solution. How much dry ferts will you need to add to add the same amount of CSM+B?

BTW I use 1/64 tsp. because the OP mentioned they add that much. But if you test and get a lower level than expected and you need to add just about 10-20% of what you orginally added, 1/64 tsp how would you add that little amount?

Now do you understand why using a liquid solution in small aquariums are a better and more precise way to add ferts. I can add a precise amount to a 1 gal tank using a liquid solution where you will not be able to do with dry ferts.


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## aquaphish (Jan 22, 2005)

onefang said:


> If you are at 4-6dkH running pure RO, then one of two things is happening.
> You have something in your tank that is breaking down under the acidity of the RO, adding to the carbonate hardness(Which shouldn't happen if you are running AS, or decently aged EC).
> Or, you really really need to replace your RO membranes.
> RO should be totally bare, IE, no kH, no GH, generally a pH around 6(or lower), and a TDS of 0 on decent membranes.
> ...


I test my water every time I make a water change to know for sure what is going into my aquarium. All parameters of the water is 0 and pH is 7.0 which is netural ) TDS 0.

So what do you think is breaking down causing the rise in dkH? Don't forget I am adding CSM+B, KH2PO4, KNO3 and K2SO4 at every water change.


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## onefang (Apr 10, 2011)

aquaphish said:


> I test my water every time I make a water change to know for sure what is going into my aquarium. All parameters of the water is 0 and pH is 7.0 which is netural ) TDS 0.
> 
> So what do you think is breaking down causing the rise in dkH? Don't forget I am adding CSM+B, KH2PO4, KNO3 and K2SO4 at every water change.


Hopefully this isn't a total thread-jack, but there has to be something breaking down. None of those ferts would add to the kH at all.
CSM+B is Magnesium, Copper, Iron, Manganese, Molybdenum, Zinc, and Boron, which also have no effect on the kH.

What you should be on the look out is for anything in your tank that could be shedding carbonates(Like any rocks, crushed coral, or calcium based anything). Perhaps your RO water comes from a system with an inline water re-mineralizer(this is pretty common), which is adding kH to the water to make it less acidic, and more palatable.


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## aquaphish (Jan 22, 2005)

onefang said:


> Hopefully this isn't a total thread-jack, but there has to be something breaking down. None of those ferts would add to the kH at all.
> CSM+B is Magnesium, Copper, Iron, Manganese, Molybdenum, Zinc, and Boron, which also have no effect on the kH.
> 
> What you should be on the look out is for anything in your tank that could be shedding carbonates(Like any rocks, crushed coral, or calcium based anything). Perhaps your RO water comes from a system with an inline water re-mineralizer(this is pretty common), which is adding kH to the water to make it less acidic, and more palatable.


OH it could be comming from all the snail shells that are left behind when they die off or get eaten by the dwarf puffer. But the good thing, it is not a bad thing going on. I always have a good level of kH.


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