You must take care to keep the bacteria in the sponge alive. Gravel on an UG filter must be cleaned with a gravel vacuum once every two weeks to make sure that no dead spots develop and start producing hydrogen sulfide. Power Filters Power filters are very good at sediment filtration, but they do not provide very good biological filtration. As long as you do not have a heavy bio-load a power filter will do the job. Canister Filters Canister filters are very popular mechanical filters that provide both sediment and biological filtration.
Canister filters do have some drawbacks.
Sometimes it is difficult to seal the lid on canister filters and they can leak. If you ever have problems with getting the lid to seal you can use Vaseline on the O-ring to get a good seal. The sand filter flow rate must be adjusted so that you do not blow the sand into the aquarium. Many owners of sand filters complain about the fact that the filters sand gets blown into the aquarium, reducing the effectiveness of the filter. A UV sterilizer can be added to the return line of some sand filters.