Just woke up to one fish floating, obviously dead, at the top of the tank. He is in a ziploc bag in the water change bucket now. Only this fish suddenly stopped eating 2 days ago. He started trying to sleep, stayed mostly in one spot, and his fins were still moving normally (wasn't struggling against current). No spots, no clamped fins, no sores, no gasping for oxygen, and his color was normal. Out of 5 fish, he/she was like the second to alpha...? lol and seemed fine. I figured if any would die, it would be the runt... So confused. They are all still fairly young. Is there something I'm missing? I'm worried about the other 4, even though they are acting normal cause this one was perfectly fine 2 days ago! : ( Any ideas? As of 5 minutes ago, AM= 0 Nitrite= 0 NitrAte= EDIT: nitrate is ten. I just did a water change on Friday night.