High nitrate/low phosphate

[Karen03]

Hello. I am using Perpetual Preservation System, the "Pro" system with two solutions -- one for macros and one for micros. I consistently have high nitrates (~40ppm) and low phosphates (often zero before dosing).
I have just ordered the chemicals to make a nitrogen-free macro solution. They should arrive in a week or two. Hopefully then I'll be able to slow down on water changes.

Here are my questions for you wonderful people with your superb knowledge and great experience!

1. I'm assuming that my high nitrates are related to overstocking or overfeeding. My tap water tests negative. With a high-tech tank, do you still use a 1" of fish per 1 gallon of water rule of thumb? In my previous planted tank (decades ago), I was constantly supplementing nitrogen. I have been surprised that I'm constantly removing it rather than adding it in this tank.

2. If I'm overstocked or overfeeding, why are the phosphates low? I thought if too much food or waste is causing high nitrates that it would also be causing high phosphates.

3. How many of you using PPS need to use nitrogen-free macro solution? Do you think it will solve my problem?

Thanks so much!!
Karen

[Karen03]

The tank is less than two months old with Tropica Aquarium Soil as substrate. Could the substrate be contributing to the high nitrates?
Thanks!

[exv152]

I used to dose PPS and found something very similar - the nitrogen levels tended to be too high, especially in a well populated fish tank. So I switched to micro dosing (for the iron), in addition to potassium and phosphates and my 125g does very well. I also found that mixing fast growing stem plants with slower growing plants like epiphites, and this tends to soak up any excesses that may eventually lead to algae.