Originally Posted by Three6s
I see more sand in saltwater than fresh I think babe Maybe the different filtering mechanisms are what make it possible.
Well, yes and no. Many, if not most SW systems use a sump, so there's an overflow near the top of the tank where fine particles of sand will never go and even if it did, would be trapped below in the mechanical media long before it ever reached a return pump.
However, if it's well washed/rinsed to remove the fines, sand should not find itself four plus inches off the bottom to get into an intake tube strainer.
Sand has the advantage, as Geomancer mentioned, of debris/mulm/uneaten food collecting on top, rather than settling deep within the cracks and crevices. This eliminates uneaten food and allows material to slowly decay on the surface or is easily removed with a hovering siphon.
Some express concerns about anaerobic regions that create hydrogen sulfide gases. Well, this is really a myth. Deep sand works just fine when it is not disturbed. There are some that are convinced they should stir deep sand to keep lower regions aerated. This is a mistake. First, beneficial bacteria take up residence in levels most suited to them and disrupting the colony impedes it's performance. Also, stirring the sand potentially mixes organic matter into anaerobic regions where anaerobic decomposition results in black, putrid materials and gases.
So if you use sand, either use only 1-2", or with deep sand (3" plus), leave undisturbed. Note: Deep sand offers greater bio-filtration capability.
Also, some sands are not well suited to deep sand. Very fine sands tend to pack and become too dense. For deep sand, I think pool filter sand, or sand with a similar grain size is best.
Also, some believe that Maylasian Trumpet Snails are beneficial in sand because they keep it aerated. Actually, MTS, although beneficial, require oxygen, so they will only exist in the upper inch or so of sand where oxygen is already plentiful.
For many reasons, I think sand, and especially deep sand is better than gravel. My 60g has 3"+ of [pool filter] sand.