I do test them, my phosphates of course show up as 0, and so do my nitrates.Do you test your tank for nitrates and phosphates? Look into running gfo in a reactor or just go pick up some media bags and put it in a high flow area after rinsing it.
I have a phosphate reactor but it isnt currently running. I had trouble that after I replaced the carbon inside it made the water super black every time i dumped it out and put it back in