I have 3 pacu in a 450 gallon tank. They have been in that tank now for 9 years. To say that this tank is too small for them is the understatement of the century. 1200 gallon tank build is in progress. I think the tank was a good size for them for about 5 years, maybe.Okay, tank is way too small. I remember reading once that when keeping Pacus, you have to give at least 1000 gallons a fish. That might be a bit exaggerated but I wouldn't keep them in any less than a 500 gallon tank.