Under Gravel filtration

[BajaReefs]

Has anyone made some sort of under gravel (crushed coral) filtration?

I’m contemplating making one with PVC with pinholes, under egg crate covered with plastic window screen.

[LotsaFishies]

Don’t do it.

They are detritus traps.

For that matter... also don’t used crushed coral. Always go sand.

[crustaceon]

Undergravel filters already exist and are mainly used in freshwater setups and while they do work, they don’t work that well. Could they work for crushed coral? Yeah, probably but is it any better than just using a siphon. IMO, it’s not worth it and the siphon will probably do a more thorough job due to having a lot more suction. Not to mention adding an under gravel filter would mean adding visible plumbing in the display, which might not look that great. Then there’s the safety issue...If you add a sump and somehow tie the filter into a drain, you’ll definitely need backup drains just in case that gravel filter clogs. You’d be better off using just a thin layer of CC (1/4”) and pointing strong enough powerheads at it to constantly blast detritus out and into the water column where your overflow or filter can catch it. I honestly don’t think sand by default is any cleaner than CC as both absolutely should be siphoned on a regular basis. The only exceptions here are fine sand which tends to keep detritus on the sand surface and bare bottom. The downside to fine sand is that it’s less tolerant of high water flow and bare bottom shows every little crumb of fish poo at all times until either your circulation pumps can swish it up if they’re powerful enough or you can’t bare it and siphon it out.


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[Squid]

Look up/hit up Paul B on reef2reef. He has the oldest running reef tank at like 45+ years and uses an undergravel filter

[BajaReefs]

Thanks guys, I guess I should have said undergravel powerhead.