He guys so about a month and a half ago I set up a 55 gallon tank for a good friend of mine. I had a high budget so I decided I was going to make it a super nice tank. His only suggestion was that he wanted sand. Everything else was up to me. So I got some stone hinge and a nice Fluval FX4 canister filter. I cleaned up the rocks and let the tank run for a month or so. I’m super careful with my fish and especially when they aren’t mine so before I put them in, I checked everything to make sure it was alright. I got him 4 OB peacocks and a royal pleco. I did a water change once a week. Water was never bad, temperature was 80, and the fish were eating. Everything was fine. Then one morning 3 weeks later, all of the fish were dead. I am experienced in the fish keeping hobby and I’m stumped. I just cannot figure out how this happened. The night before they all were fine, all ate. I have talked to a few close friends of mine who are also into fish keeping and they just can’t figure it out either. I want some opinions on what you guys think happened because this is just bizarre.