because of the kind of fish I keep and the fact that I am slightly overstocked, my nitrates are always too high. I try to never let them get over 60-80 ppm
My porcy will stop eating if hes unhappy. For instance I left the lights on for 3 straight days (without realizing it) and he wouldnt eat for the next couple of days. If you have changed the enviroment, temperature, salinity, ect ect.. that might be why hes on his hunger strike.
I would do mulitple water changes as cj suggested and the garlic extract has always worked for me as well.
Good luck, hope he gets his appetite back