Glad you mentioned sponge filters. They are very effective for the price. They really amaze me, and when needed you can easily move them from tank to tank. Can also move them to a brand new tank to use as an isolation or hospital tank. http://business.accesscomm.ca/ultimatesponge/ These are very cheap, and very effective. 4 of them will filter a reasonably stocked 55 gallon tank with no problem.Originally Posted by rfeiller