PMDD ~ What’s the function of SO4 in a planted tank.

[Plantbrain]

It's correct, I used Epstein's(1972) dry weight for my reference.

I double and triple checked my ratios required for roughly the 4 times referenced amount of N vs K.

This also assumes no K comes from fish waste/food.

The simple test is does it work or not, addig K2SO4 will not hurt, so you can add that if you wish still, but adding it will not help unless you have a large fish load/less light etc, George Booth did/does, Discus in a lower light CO2 enriched tank. So he likely has a need for K2SO4.

I tend to have low fish loads, sometimes none at all, to see what specific nutrient issues arise.

But some references to my ratio and usage of KNO3 as the sole source can be found on the APD and also Aquaria central's plant forum here:
http://www.aquariacentral.com/forums...ad.php?t=21033

So if you want to check the math and chem, be my guest.

Regards,
Tom Barr

[hobbit6003]

Guys,

Salts do not react with one another.

Cheers,

Kenny

[Anubias]

My understanding is that the ratio of 1.5:1 is a ratio of nitrogen to potassium by weight. In this case if half of the nitrogen comes from fish food and decay and half comes from the addition of KNO3, then there is available twice as much potassium as one needs. I guess that it all started with the introduction of the Sears and Conlin PMDD formula.

Assuming neither potassium nor nitrogen in the water supply, solving for X in the formula 61X2-178X+89=0, where X equals the maximum percentage of nitrate produced by organic processes and where 1-X is the percentage of nitrate to be contributed by adding KNO3, yields a situation where K and N are balanced. This point is near where approximately 64% of the nitrate is coming from decay and 36% from KNO3 addition. Beyond this point, one must add potassium in a form other than KNO3.

One of you science guys can check this out as I have grade ten chemistry and not much more math.

Regards,

[Plantbrain]

Make sure you use elemental N and not NO3 and P and not PO4 etc when you do the weights.


Regards,
Tom Barr