Whats a plenum filter?

[jim27]

Someone please explain to me what it is, how it works, and if its a good filter or not.

 

[mr . salty]

A "plenum" is really not a filter at all.It is more of for nitrate reduction.It consists of some pvc tubes laying down under a couple layers of sand.With screen separating the layers...Are you talking about an Under Gravel Filter(UGF)??? If so,these are no longer the reccomended filter method for a marine tank...A sump-wet/dry,or hang on the back(HOB),or even a canister are better than a UGF...