Depending on the filter you have, it may not actually be too high of a flow rate. The Aquaclear 70 is rated @ 300 gph , and although it's suggested for 70 gallon tanks...it has been successfully used on smaller setups. Flow rates tend to be over rated by manufacturers and measured under better than "normal" conditions anyway. Many HOB's also have some way to regulate flow as well, so you may not have to go with the max flow possible. Try it out...watch your fish...They will tell you if flow is too high by their behavior.