My gf has a Emp 280 on a 20g high tank. She has some really small guppies and they seem to do ok with it. It does really make the water flow but the fish are able to handle it. The penguin 200 maybe better for a 15g though. What kind of fish are going it?noddy said:I don't think he wants to use a sponge in the tank. Would an emperor 280 be to much? I know that the 400s do a deccent job, but would be overkill.