Aquarium Power Filters
The filter of choice for the larger aquarium (20 gallons +) is the power filter. This is a filter that pushes water directly through a filter medium by means of an impeller that is mounted on a round magnet and driven by another round magnet on the driveshaft end of an electric motor. Separating the motor and the impeller is a plastic wall that keeps the motor away from the water. There are many brands on the market. The one you should buy is the one your local dealer can service; service and spare parts are the deciding factors in which brand to get. Certain of these power filters have rather special filtering media, one of which is diatomaceous earth. These so-called "diatom filters" have proven to be very effective in keeping aquarium water very clean.
