Bioballs are best used out of water with water trickling
over them. They do work under water, but do their best
work out of water with water trickling over them.

For reef tank, just use live rock and live sand filtering,
and a protein skimmer.

Wayne Sallee
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I've already got crushed coral as substrate. I don't really like the way
sand blows all over the rocks and stuff. Would it work to add a couple
inches of sand, mix it together?

Cindy