I have 7 small veiltails (I may go up to a larger tank in the future, but just have them in a 37 tall for now) in a topfin 37 'kit' tank. The filter it came w does 40 gallons but I don't think it will be enough for messy goldfish. I was considering putting a marineland biowheel HOB 350. (supposed to do 75 gal tank) Is that too much? I am worried with these fish who are sometimes weak swimmers that the current it creates may be too strong. 2 of the 7 are orandas and I noticed they don't seem to be really strong swimmers in current. I think the filter it came with is too weak of a pump to draw water from that depth throughout the entire tank.