Oh boy.. my stock solutions for KNO3 and KPO4 are both 1M concentrations.. and I think I was dosing two or three ml's worth every other day, enough to get PO4 to 0.25 mg/L and nitrate to 10mg/L. But dont quote me on that.. you
can quote me that the grass was sucking down an average 80mg nitrate and 5mg phosphate per day.
I have now switched to using Seachem Fluorish Nitrogen.. originally made for freshwater planted tanks.. and dose 5ml every other day. That's enough to get to about 4.5mg/L nitrate and the plants blow through that in two to three days.. so, actually, if I do the math, the bed of grass has started to consume even more nitrate.. around 95 mg each day. Phosphate is also using a Seachem Fluorish mix.. and has also come up, about 6 mg each day.
Dosing nitrate definitely does reduce phosphates. If the plants have nitrate available then they are able to uptake the phosphates in the system via growth. No nitrate, no growth, no phosphate uptake.. they've gotta have it.
In fact, if I let my nitrates fall to zero, I get nuisance algae outbreaks usually. I got my tank to recover from this phosphate OD by doing only a little scraping of the front glass, a slight water change to remove some of the excess phosphates, and bumping up the nitrate levels pretty high to about 30 mg/L. I could do that safely at the time as I only had some grass shrimp for livestock. More nitrate, more growth, less evil phosphate.
>Sarah