I have read the recommendation is for about an inch of sand for substrate. Has anyone tried, or even thought about a plenum. I have tried this for a reef tank and I am happy with the results, but this isn’t a reef, it’s an octo tank. The setup I’m talking about is described in detail at garf.com. Basically there is grate covered by plastic window screen to create the air pocket, then 2 inches of reef sand on top of it. This is covered by another screen, then a couple more inches of reef sand. This second screen keeps burrowing critters from going any lower. Will this be ok for a bimac, or do you think I should just go with 1 inch of sand?

Go with the 1 inch of sand - your octo would find a way to tear it the arrangement you describe.

Nancy

Its pretty much the same as an undergravel filter except you remove the powerhead when nitrites are 0.

I have a few set up on my tanks. An octopus would tear it apart for sure, dont use one.

Hi tony, if you want to try a plenum then maybe set one up in a sump plumbed into your main tank, a plenum or DSB in an octos ank wont last long at all.

cheers
colin