crushed coral with sand

[eddie]

Since I have set my 150g tank up about 2 years ago, I have had what I think is sand floating around all the time. NO, it is not air bubbles. I have been thinking about putting crushed coral on top of the sand. Any thoughts? Any preference on substrates? I have reduced the flow and it doesn't help. It is like dust suspended in the water.

[eddie]

Can any one think of a down side?

[Wryknow]

The crushed coral should be OK to put on top I suppose. Denser sand should naturally be compacted at the bottom of the tank via gravity but I'm not 100% certain of the weight density of silica sand vrs crushed aragonite (and of course, any burrowing organisms might turn the sand over at any time.) I'm guessing that you have a fine, silica based sand now? If so, I would really recommend doing a substrate change if at all possible. You might also consider just adding some mechanical filtration to polish the water up a bit.

[Richard]

Crushed coral tends to trap lots of detritus. I would use something a little smaller like carib sea special grade aragonite.