There is no need for vac. if the sand is full of worms and pods. In fact, it is better to leave it alone instead. For crushed coral, particular for some of the coarser one, you may want to vac. it only for the sake of look/appearance. IMO, vac. sand only if you have a UGF, which is rarity nowaday in marine tank.
Never vacuum true fine sand in a salt aquarium with live rock. If it's not live enough, or gets icky looking, get some sand with worms and live stuff in it to seed your tank. Some say use a sand sifter, but I wouldn't unless you have a dead sand bed and want to keep it that way...
I keep hearing this, and i have in my 55g a sand sifting star,
and I have tons of tracks from worms and burrowing pods.
After the lights go out, the sand bed is crawling with life.
For a while i was going to get rid of the star, but i figured why bother?
I have the similar question. How do you seed a sand bed and why do you do it? I have been vacuuming everytime I do a water change, about every two weeks. I thought a light vacumming of the sand helped to clean the "goo" from the tank. Is it best to just leave it, am i sucking all the "good critters" with the gunk?
Seeding is done by adding a cup or two (or more) from an existing tank (that has an active sandbed with worms/pods). If you have a reef club in your area, chances are real good someone in the club can help point you in a good direction there...
As far as vacuuming, if it's a fine particle bed you're better off leaving it alone and just getting it seeded with live sand.
If you get a buildup of diatoms/algae/cyano on the bed you can add critters to help maintain it. (Like trochus snails, a conch, or cuke.. - sand sifting stars are sometimes controversial as to whether they munch too many pods, but I think that's mostly a matter of how big your tank is and how it's scaped. - If there are places pods can hide/thrive without being over-eaten..)
DeadHead, The reason for seeding the sand is to introduce the micro critters that are not present in sterile sand (dry sand or crushed coral).These little critters love to consume the waste that falls to the sand floor. Hope this helps!!