New 73 gallon tank setup

[Frogger]

Changing water about 10 gallons every second week on a 80 gallon system. This was more an effort to reduce phosphates that had gotten really high. Using only RO DI water newer filters. I was only lightly feeding and have a low fish bio load (5 fish). I was using a lot of GFO to help reduce phosphates. I have never registered Nitrates. It was Gregzz4 that told me the 0 nitrates is the problem.