Mysterious Tetra Die off
I have a 29gal tank that was stocked with 17 tetras, 2 corries, 2 guppies, and a breeder box with 6 guppy fry about 5 days old.
Planted tank, 30gal filter, Heater: 78-80F, and airstone.
I found a dead tetra Wednesday night and I took the poor fella out. Thursday (yesterday) another had died when I came home from school. I took him out and did a water change. I sat around the tank and did homework so I could keep an eye on my tank. Everything was normal, I had active fish, no external or behavioural signs of illness, and then 1-2 hrs later another tetra drops dead. As of today, I have lost 5 total. I can't figure out why they're dieing. I got them (12 of them) about a week ago from petco. They were freshly shipped. Anyone have any ideas of what I can do? Water tests fine, A: 0 Nitrite: 0 Nitrate: 5.