KH2PO4 . help. - The Planted Tank Forum
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post #1 of 7 (permalink) Old 03-27-2013, 08:53 AM Thread Starter
Algae Grower
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KH2PO4 . help.

according to calculator : 1 Litre of KH2PO4 mix with 1 litre of water , that will be 1 litre of phosphate solution which gives 1.68ppm of phosphate in 110gallon.

lets say , i dose 1 litre of the solution in 110gallon my tank phosphate level will increase by 1.68ppm . But how should i dose the phosphate solution weekly in my 110 gallon ? and how many times in one week ?
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post #2 of 7 (permalink) Old 03-27-2013, 09:34 AM
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I am not sure what values you are using for calculating your dosages, but 1 litre of potassium phosphate?

You will want to mix up a more concentrated solution so that you are not dosing 1 litre of liquid at a time.

For dosing, I would suggest you do it 3 times a week, but ultimately, it depends on what fertilization regimen you want to follow as well.


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post #3 of 7 (permalink) Old 03-27-2013, 09:43 AM Thread Starter
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lets say im doing 3 times a week. So how much water should i mix my kh2po4 with ?
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post #4 of 7 (permalink) Old 03-27-2013, 11:20 AM
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What's the concentration are you trying to acheive? It also depends on what kind of fert regime you are trying to follow and what type of regime will depend on your light and co2 setup.
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post #5 of 7 (permalink) Old 03-27-2013, 11:34 AM Thread Starter
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maintaining 1-2ppm is what im trying to achieve.
my 10lbs pressurised co2 is maintaining at 25 ppm. Having 4x54W parabolic reflector for every tube. Although in terms of WPG , i have below 2 , but im 100% sure that most of the light made it into the tank. So High- Light.

According to Rex " For dosing KH2PO4 you need to mix 7.2 grams or 1.5 teaspoons or 0.50 tablespoons into 250 ml of water. Each ml of this solution will 0.53 ppm of PO4 in 10 gallons of water. "

say , mine is 120gallon tank water. Does that mean i will need 12ml of the solution to raise 0.53ppm of PO4 ?
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post #6 of 7 (permalink) Old 03-27-2013, 04:22 PM
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Using this calculator:

I see that 1/4 tsp of KH2PO4 will yield 2.15ppm of PO4 in 120 gallons of water as long as you are dry dosing. If you have a solution already, then it depends on the concentration of your solution.
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post #7 of 7 (permalink) Old 03-27-2013, 07:50 PM
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Depends on the teaspoon and the type of KH2PO4 I believe. Several different masses will = different amounts depending the the source.

The old days, everyone got their KH2PO4 from the same place.

So mostly the tsp error was the issue.

I'd add about 3/4 tsp 2-3x a week personally to a 110 gallon tank fully planted with good light etc and rich CO2.

Less if you have poor CO2/algae/lower light etc.

Ferts are VERY easy.
The most difficult thing to dial in correctly.

Tom Barr
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