My two week old bristlenose fry are having trouble today. About 10 dead just today. They are in a 10 gal grow out tank by themselves. The tank was cycled with a bottle of stuff from API, molly fish. Water tested great after three weeks with the molly fish and still good. Feed them cucumber yesterday and little flack food. The tank gets a 8L change each day out of 38L tank. There is a sponge filter and heated to 26 degrees.