Post by Cyberguppy on Jan 29, 2006 21:14:03 GMT 10
These filters usually sit either within the hood or on the back of the aquarium, they draw water out of the aquarium, run it through an exposed filter media then return it to the aquarium. filtration from these kinds of filters is mainly biological and aeration is also provided from the water flowing over the exposed media and usually through a spray bar back into the aquarium. these can vary from very gentle to quite strong filtration.
