I set up a 20 gallon the other day. I asked my wife to pick up 2 cheap fish to cycle the tank. I was expecting two guppies or goldfish. She brings home two angelfish. My wife means well. I come home today and find the one stuck to the inlet tube on the filter and the other laying on the bottom. There goes $7 down the drain. I was adding a product called biozyme. The NH3 and NH4 levels are 0. I'm not sure why they died.