That depends on what kind of power filter you want. I personally prefer Aqua Clear's but alot of people like the Bio-Wheel Filters. You can get power filters that will filter up to 500 GPH (the AC 500) or as low as 100 GPH (AC Mini). Power filters are pretty cheap if you know where to get them. There cheaper on the internet that in your LFS. The most expensive ones will be about $55 to $60. You could find them Here.
