Plenum and Undergravel filter

[myazid]

What the difference between a plenum and UGF?

What benefit by having a plenum in a reef tank?

[slipknottin]

a UGF forces water through the substrate. it provides a mainly aerobic (lots of oxygen) and will give you a large surface area for aerobic bacteria (which convert ammonia to nitrates).

plenums are grids set up on the bottom of the tank, and are covered in a thick layer of fine sand. they have no forced water flow through the bed, and the bed becomes mostly anoxic and anaerobic (low to 0 oxygen). here bacteria that convert nitrate to nitrogen gas develop.

the american adaptation of the plenum system is the DSB. a deep sand bed, made up of sugar sized sand thats 4"-6" deep, and doesnt include a plenum space at the bottom.