Hi, I'm Nina new to this website thing lol. Um I need some advice. My boyfriend has a 10 gallon tank and had 3 l fish idk exactly what kind though. Anyway he just got a sucker fish from Walmart. I believe they're called "plego's"? It's been about 3 days since he got it and it was fine with the other fish but today he looked in the tank and saw all 4 of the fish are dead. And 3 of the fish have white stuff on them except for one. Can anyone help my situation we're so confused.