I started a freshwater tank about a month ago and stocked it with a few neon tetras, some glofish, and eventually a few african dwarf frogs, a suckerfish and a snail(both to combat an outbreak of white aglea that Im still trying to avoid using chemicals to control). I put the tetras and glofish in first to get the bio filter going, and after a few days when the ammonia and nitrate levels were undetectable i added two angelfish. When I added them I had a bit of an ammonia spike for a day of so but it went back down to undetectable levels. About a week later one of the angelfish died during the morning while i was in class. that morning it seemed healthy and active, and showed no signs of being ill. About two weeks later i lost the other one, same story. It died in the night, once again no signs of illness the night before. I checked that water quality both times, it was fine. Any reason they might have died? the tetras and glofish which ive had from the start are still thriving, as are the other creatures that ive added. I want to try adding angelfish again, but i want to find out why the first two i had died before i try adding any more.