[Woodstock]

Yes, you can have too much/too little flow. Low flow is unhealthy for the tank inhabitants but too much flow can tear tissue or keep a coral from opening up fully. SPS tanks require higher flow thus are usually BB but softie/LPS tanks only require medium flow so they usually have a sand bed. I have 3" sand beds in both my tanks and keep primarily softie/LPS. I have been BB before but prefer the SB for its looks and NNR properties. To preserve it and keep it from blowing into piles, I tweak the flow by creating random currents using a wave maker. Although the flow is not 20x like Gina's, I do get good flow without blowing the sand away. To create turbulance yet avoiding linear blasts of flow, I try to point the returns/power heads towards eachother or bounce the current off of the side/rock/or water surface.

For those of us that use PH, another way to eliminate linear blasts is to use tunze. They are made to create very wide flow zone that spreads the water flow over a much broader area. These units are very pricey but there are modifications available that will turn a modest maxijet from a narrow jetstream into an awesome wide flow unit comparable to the tunze. I saw such a modification on Chad B.'s (reefscience) huge frag tank. He made it sound easy but I've not tried it yet. I'll get the information together and post it soon....