well, there's a few ways to go. that is a good amount of fish in a 10gal tank. if you can maintain water quality as it is you dont really need anything additional. having said that, another filter of any type will give more area for beneficial bacteria, and promote some more water flow. now here's what id really recommend. watch for a dollar a gallon sale, and snag yourself a 20gal tank when you can, keeping the 10 for a backup or QT tank.