Many people recommend the Fluval Series canisters. You want to get a filter that cleans a tank two to three times the size of it—so if you have a 75 gallon tank, you need a filter that cleans between 150 to 225 gallons (turtles are VERY filthy, so this is needed if you don’t want to clean the filter every week or two). You want to look at the capacity the filter cleans, NOT the GPH (gallons per hour). It’s often in the description of the product, not the title.