[Myka]

What type of corals do you have?

Generally, BB is an SPS thing because low nutrients or ULNS is easier to achieve with no sand and also because of the super high flow used in SPS tanks where sand might blow around too much. My SPS tank is mostly BB, just a bit of sand remnants dusting here and there. When I eventually get the new tank moved in I will be using white starboard on the bottom (HDPE sheeting) which I think looks nicer than glass and also helps protect the bottom pane from rock slides.

If sand is used, I prefer a coarse sand like the CaribSea Special Grade. I also like to use only 1/4-1/2" of sand or at least definitely not more than 1". This way it is ok to use a gravel vacuum to vacuum the entire depth of the sand to keep it quite clean. IMO there is no point in having more than just a skim layer unless you're doing a DSB. A DSB should not be disturbed by vacuuming (or sand sifting fish!) at all.