Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
From the link in post #7, Analysys of the root tablets.
Note: I do not see and phosphate here. There is N, K, Ca, Mg, Fe and traces.
"Chemically Active Ingredients: Hydrated Magnesium sulfate, Potassium nitrate, Potassium sulfate, also trace amounts of; Cobalt EDTA, Copper EDTA, Iron EDTA, Magnesium EDTA, Zinc EDTA, Manganese sulfate, Sodium Borate, Sodium Molybdate, (Chelating Agent: Ethylenediaminetetraacetic acid)
Physically Active Ingredients: Calcium Carbonate (CaCO3) Magnesium Carbonate (MgCO3) Calcium Carbonate Equivalent (CaCO3) Calcium Sulfate (CaSO42H2O)"
From post 8:
Picture 2, 3, 4: Does not look like Diatoms or potassium deficiency. More like mechanical damage.
Picture 6, 7: Looks more like what I have seen as mechanical damage or potassium deficiency. Snails and other livestock may not be able to rasp healthy plant tissue and do much damage, but if the tissue is compromised then they can rasp holes in it.
What are the current parameters for NO3?
Based on the fertilizers listed I think the only significant supply is the fish food. The root tablets might be pretty low, unless you used them at the maximum rate. Even then the slow release means the N and K are mostly unavailable, locked up in the tablet.
Seachem Comprehensive is very low in N. Really, just a micro supplement.
Anyway, I would dose macros in the water column. See if that helps.