Plenium? Question

[dralarms]

One of my lfs (next city) has egg crate with fiberglass screen glued to it under his sub. in his tank. I have to ask why? Is this a pleniuim? If so how does it help the tank and would it be a good idea to put it in my 150 (taking into codsideration I have to dismantle it 8O ). I would be willing to do it if the benifits outweigh the labor, It wouldn't be really hard, just take a little time.

[RMPD109]

That would be considered a plenum. It functions the same as a DSB. It provides a location for denitrifying bacteria to grow. To function properly the oxygen levels must be greatly diminished. You would still need a good sand bed to get the low oxygen levels.

[dralarms]

So, I could remove my sand, place the "plenum" in place and put my sand back and it would be a good thing for my tank? Cool

[RMPD109]

If you already have a DSB you are getting the benefits of it now. The plenum will not benefit it much more and can collect some detritus over time.

[dralarms]

My sand is not 4 to 6inches deep so it's not considered a dsb, right? I have watched air bubbles rise up from my sand for some time now. Nothing close to an area and I'll get a bubble from the sand, what causes this?

[cmor1701d]

Correct, a DSB is 4" or more. Mine is 6-8". Instead of removing everything to make a plenun why not increase your sand bed depth. Add about a ½" at a time, leave it for a couple of weeks then add another ½". Repeat till you get the desired depth.

The bubbles you are seeing are gas created by the decomposition of wastes in the sand bed. The bubbles could be ammonia gas or hydrogen sulfide or even nitrogen is the bed is deep enough. Nitrogen gas production is the goal of the DSB.