When I removed my deep sand bed and went shallow I began turning that excess sand into frag disks. I've made around 80 large ones and over 200 little ones so far... and I still have a lot of extra sand. Obviously you'll want to rinse the sand as well as you can first.

http://www.canreef.com/vbulletin/showthread.php?t=59760

It's definitely some kind of ugly when the sand first comes out. Still trying to get used to the look of it, but I'm sure it'll look better when the coraline starts. Super cool how I can direct flow anywhere I like now. For that reason alone I think I'd find it difficult to put the sand back in.

I'm having a lot of trouble getting the last bit of sand out from between the rocks, and the sand has caked along where the rock meets the glass so it has to be chipped out. So for the next little while it looks like I'll be blasting with a power head and siphoning :cry:

You will likely have to do this on a regular basis anyway as the debris will tend to collect in a certain area of the tank with the flow.

I know the typical mantra is that BB allows you to push more flow through your tank and that's certainly true - you can without the risk of sand blowing around.

With that said, I've recently reduced the flow in my BB 24 x 24 tank and noticed a significant improvement in growth rate. Previously I was running around 75X my tank volume in flow and now I'm down to around 55X. I may be in a unique situation given how small my tank is and the fact that most of my corals are mini colonies and not large colonies yet. The smaller corals probably aren't impeding flow as much as would occur in other tanks or with larger colonies. But just because you can get away with running more flow in a BB tank doesn't mean it's the best decision.

I have a few theories on why reducing the flow has helped my tank. The primary one being that the lack of sand and my open rockwork minimizes the scrubbing of flow velocity that occurs in tanks with sand where the sand scrubs some of the velocity of the flow. Of course it may also have something to do with slower flow allowing the coral polyps more time to capture some food.

Interesting you're getting better growth with less flow. I was under the impression you can't have too much flow in an SPS tank, unless a nozzle is pointing directly at a coral. I know corals will alter their growth form, growing shorter and heavier in a very turbulent environment. My Yellow Slimer was doing this until I switched to a flare nozzle on my Wavy Seas.

Definitely better flow around the rocks at the base without the sand. With the sand covering it I'd forgotten how open my rock work is at the bottom. Not sure how much the texture of the sand itself impedes flow.