Tile, eggcrate, and anaerobes

[carpguy]

I just wanted to run this past you folks.

I went out over the weekend and collected some driftwood. I decided to silicone the wood down to some 12" square tiles. Since there will be rocks on top of the tiles I decided to keep the eggcrate underneath, almost completely covered by the tiles. Once the silicone is cured I'm going to move the substrate back on top of the tiles. I'm figuring the cells of the eggcrate will flood, but since they're empty I'm hoping to avoid any problems from anaerobes. Does this make sense? Would I be better off without the eggcrate? I don't want to have to tear this down again…

[wetmanNY]

Since the eggcrate will flood, bit by bit over the months substrate will fall though the grating and fill up the spaces. That may cause awkward settling of the substrate, visible from above. So, to get around it, once the eggcrate's permanently positioned, I'd either fill it with coarse unenriched substrate before the stones are set on it or wrap it with landscape cloth (weed-proof), to keep the undergravel space from silting up. Essentially you'll be creating a kind of freshwater plenum under there, whatever you do.

Could be some longterm nitrate reduction for you as a reward for your troubles...

RTR may have some experienced recommendations... RTR? RTR?

[carpguy]

I was thinking that if the cells are filled only with water there wouldn't be all that much surface area for the anaerobes to colonize. I've got three 12"-square tiles in a 30g, so they're covering up pretty much all of the eggcrate -- I don't expect much in the way of settling or infiltration.

Would I be better off, plenum-wise, filling the cells with the rough sand substrate before capping them with the tiles? Since they'll be more or less permanently out of the way, should I be concerned about the anaerobes? Are the toxins only a problem when they're disturbed?