Potassium Nitrate & Phosphate Connection?

[freshgoby]

First let me say that I'm just starting to work with my tank and understand its fertilizer needs.

On the 24th I dosed a ½ tsp of potassium nitrate to my 50 gal. The nitrate levels went up to 10 and have stayed there for the past 3 days. I'm guessing they haven't gone down because I haven't added any phosphate and the ratio of phosphate to nitrate and potassium is too low for the plants to actively use the nitrate and potassium.

Is this a correct hypothesis?

 

[VaughnH]

If you haven't calibrated your nitrate test kit, you can't be sure of your measurements. But, it is certainly true that plants will consume a lot more nitrates if they are also supplied with phosphates. People who have been under-dosing phosphates, and who then increase that dosing, report that they tend to run short of nitrates pretty quickly. Part of that is a temporary effect, but not all of it.