no sand bed totally depends on the amount of flow you have, and how much live rock you're tank has...
there's a balance that has to be maintained... a deep sand bed works better with low flow over the top of the sand... live rock works better with more flow going through it...
so...
you can either have a ton of live rock in the tank, and medium flow, or have a small amount of live rock but with a ton of turbulent flow... i'm going to go barebottom soon (been saying that for like a month now
lol) and i'm going to go with a moderate amount of live rock, with a moderate amount of flow since i have some delicate LPS pieces...
also... you can rock a RDSB if you are unsure about going sans DSB... there are plenty of DIY writeups online... google RDSB or remote deep sand bed...
IHTH...