My advice is to stay about 4" on the DSB
. I've had tanks with DSBs and heavy bio loads and have nero nitrates, and other's with low bio loads that have high nitrates. I've also seen my share of tanks with zero sand bed and no nitrates either, so the verdict is still out for me. I give the hedge to DSBs actually working, but I'm simply learly of those super thick DSB
's that seem to encourage a crash.
Use live sand as uch as possible. Not because it's "live", but because it's about a billion times cleaner and easier to work than raw sand or ooltic. Dry sand will take months to compact and not cloud up the tank when it's looked at funny, so be warned. The trick with a DSB
is to encourge a waterflow directly across the top of it which seems to help with gas exchange. DSBs in tanks with high current rates only at the upper levels (a bad habit with many reef keepers) don't seem to work as well.
Triggers could care less about sand beds, and will actually enjoy digging in it. Triggers also differ in behaviour. The Huma-Huma (Picasso) is in my experience a roving terror on anything soft or hard that moves or crawls. They also have a habit of munching on live rock and knawing on plexiglass tanks if bored to keep their teeth in good shape, but they are also among the most intelligent of all fish species and most personable. The clown trigger is not that much better, and the black trigger being the mildest of the group and least risky in reef/invertebrate tanks.