# KH2PO4 and K2SO4



## paul236313 (Jul 23, 2004)

I'm going to try using powder fertilizers for macro's and i wanted to know the difference between KH2PO4 and K2SO4.I know about KNO3 for nitrates.Which of these should i use for phosphates :?: and what about Magnesium Sulfate and Calcium Carbonate..do i need these as well :?:


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## Error (Apr 16, 2004)

K2SO4 is typically used to add only K+ to your water column. KH2PO4 is for PO4 and a little bit of K+.

I wouldn't worry about your Ca/Mg situation until you've got your macros situated well.


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## paul236313 (Jul 23, 2004)

I was getting the macro's down pretty good with my liquid ferts.I was using Flourish Nitrogen,Phosphorus but i noticed alot of you guys like using the PMDD.Now im starting to learn why its alot cheaper and easier when to maintain dosing levels.As far as you tom mentioned he said 10-1 ratio for KNO3 and K2SO4.Does that mean 10 teaspoons of KNO3 and one teaspoon of K2SO4 :?: and how many ml's should that be mixed with.Just a beginner here please be patient


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## Error (Apr 16, 2004)

I think Tom might have been referring to KNO3:KH2PO4 as opposed to K2SO4.

Use the fertilator (the chemicals in question are Potassium Nitrate for nitrate and Potassium Phosphate Monobasic for phosphate) to calculate your values. A 10/1 ratio for Nitrate/Phosphate is good.


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## plantbrain (Jan 23, 2004)

Yep, not K2SO4.

I've generally not used K2SO4 for awhile. 
Steve Dixon talked about this to me about 7-8 years ago(not adding any K2SO4) and getting it all from KNO3.

He was right then, still right today.
You'll virtually always have more K relative to N, without the K2SO4.

As far as a ratio and that business, ratios are not that important until you get to the point were something becomes limiting. 

It might be deemed wasteful I suppose..........and it makes a nice dosing discussion, 10:1 etc, but I cannot find any real argument to suggest it something important to tell someone.

It may make dosing somewhat easier for some folks and allow estimations easier, but the plants just need enough, not a particular ratio really.

I can add .2ppm of PO4 and add 20ppm of NO3 and also add 2ppm of PO4 and 2 ppm of NO3 and have similar results, as long as the dosing is done consistently.But you might need to dose daily for the PO4 with higher light tanks.

But a lesser extreme of say 2ppm of PO4 and 5ppm also works just fine is well off the 10:1 ratio. That level vs .5ppm PO4 and 10ppm NO3 will do no harm.

Regards, 
Tom Barr


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## Edward (May 25, 2004)

paul236313 said:


> Now im starting to learn why its alot cheaper and easier when to maintain dosing levels.


Generaly speaking, 10:1 means ppm of NO3O4 ratio. To do this, use dry weight ratio KNO3:KH2PO4 of 11.4:1.0 . This will make plants grow well, but K deficiency will leave some NO3 hanging in the tank. Reseting the tank by water change disposes the extra NO3. Time to repeat the dose again.

If you want to maintain stable water column ratio NO3O4 of 10:1, you need to use dosing ratio of 3:1 plus extra K. To do this, you can use ratio KNO3:KH2PO4:K2SO4 of 48.4:14.2:37.4 by dry weight.

Dose every day very small quantity. On the end of the first week test water in the tank for NO3 and PO4. If too high, lower the daily dose. If not enough, increase the daily dose.

By dosing every day you never run out of nutrients.

Edward


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## plantbrain (Jan 23, 2004)

Edward said:


> paul236313 said:
> 
> 
> > Now im starting to learn why its alot cheaper and easier when to maintain dosing levels.
> ...


It depends, you can dose 2-3x a week still not run out of nutrients easily, this is done by knowing the max growth rate/uptake at high light, at less light, the plants will use less and they will have enough N, , K etc.

This has some limits but you don't gain anything as far as the plants are concerned dosing daily vs 2-3x a week.
Your habits might be troublesome(did I dose today? or yesterday or???), but the plants don't care as long as nothing runs out or gets too low.

NO3/PO4 are cheap, so wasting a little and erroring on more rather than less or such tight control is not something I would suggest, you'll screw it up and stunt your plants the close you get to adding "Just enough".
Maybe not today, but later. And there is not much gained from it as far as the plant's and algae are concerned. 
I've done this for years in the past.

This is one reason I'm sort of leary about ratios, I know the ranges of these ratios, rather than some "specific" ratio. It's fairly wide ranging.

I am not sure what you mean by K+ deficiency, unless you have 75% of your N coming from fish food/waste, the KNO3 alone should be enough to supply the plant with K+, so the dosing of KNO3 will almost always result in excess K+ relative to the plant's needs.

Even a loaded Discus tank that's well fed did not need any K+ added using KNO3. 50% of the N came from fish waste.

You can see the post about this on the APD or AC about dosing KNO3 and not needing KCl or K2SO4 etc.

Regards, 
Tom Barr


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## Edward (May 25, 2004)

> It depends, you can dose 2-3x a week still not run out of nutrients easily, this is done by knowing the max growth rate/uptake at high light, at less light, the plants will use less and they will have enough N, , K etc.


Yes, when plants get use to the stable environment, the tank becomes so predictable, dosing 3 times a week becomes sufficient. But stil the highest uptake is achieved by more frequent dosage.


> This has some limits but you don't gain anything as far as the plants are concerned dosing daily vs 2-3x a week.


Right, plants are still happy.


> Your habits might be troublesome(did I dose today? or yesterday or???)


No need to dose every day, you can skip no problem, this is not about keeping NO3 at 1 ppm. This allows to maintain any NO3O4 ratio and any level. It's everybody's choice what to keep it at, 5.0:0.1 or 40:4. It's like a car running on a cruise control, you chose the speed and the gas keeps dosing.


> but the plants don't care as long as nothing runs out or gets too low.


What element is not sufficient at low concentration?


> NO3/PO4 are cheap


It's not about cost, it's about time and enjoyment of a tank with water in it. 
We don't feed fish 1 lb of flakes a day and then do water change to clean it up.


> ...you'll screw it up and stunt your plants the close you get to adding "Just enough".


Perpetual Preservation is not about Just enough, but about maintaining high levels of nutrients, full spectrum.


> I know the ranges of these ratios, rather than some "specific" ratio. It's fairly wide ranging.


Plant uptake ratio is different at weekly dosing then at daily dosing.
You have changed your dosing from weekly do daily lately, days 1 3 5 and 2 4 6, why?


> I am not sure what you mean by K+ deficiency, unless you have 75% of your N coming from fish food/waste, the KNO3 alone should be enough to supply the plant with K+, so the dosing of KNO3 will almost always result in excess K+ relative to the plant's needs.


A test by daily dosing of KNO3, KH2PO4 and K2SO4 showed higher NO3 and PO4 uptake then KNO3 and KH2PO4 dosed alone. The plants were able to uptake more nutrients with increased K. This was a Perpetual Preservation test that keeps stable levels. Surely K deficiency is not an issue with over fertilize and water change system.


> Even a loaded Discus tank that's well fed did not need any K+ added using KNO3. 50% of the N came from fish waste.


The K test was done on a tank with no fish and a tank with low load fish. Same result.
I am not happy about the necessity of additional K, but the tanks were on hold with plenty of NO3 and PO4, going nowhere for two weeks. Small doses of K2SO4 made the NO3 and PO4 disappear.

Thank you for your time,
Edward


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## plantbrain (Jan 23, 2004)

Edward said:


> Yes, when plants get use to the stable environment, the tank becomes so predictable, dosing 3 times a week becomes sufficient. But stil the highest uptake is achieved by more frequent dosage.
> 
> 
> > Are you sure about that????
> ...


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