Equipment Review and Discussion :: Question about different kinds of filters

[Shorty's mom]

This may be a dumb question but.... what is the difference between a canister filter and a wet\dry canister filter?

[steve]

This is part of the EHEIM description.... "The water movement within the filter is bi-directional allowing for extended contact time between bacteria colonies, oxygen, and toxins, which are thus decomposed much more rapidly than in a traditional filter. Decomposition of ammonium and nitrite is faster. Exchange of oxygen and CO2 is accomplished by means of displacement through the specially designed breathing tube."

I've seen other wet/dry filters that expose the bio media to air and the water flows over them. I'm sure there are a few other methods to accomplish a wet/dry definition.