I have two 6025's in my 3 foot 65 gallon, and it is plenty of flow. However, mine are modded so they do push more water than a stock 6025. The mod is very simple, all you do is remove the ******** housing around the impeller. The only downside is occasionally they will suck water in when you first start them up instead of blowing it out, but all you have to do is put your hand over the outlet for a second or two and it reverses the impeller.