The reverse carlsons don't seem to do much.... I've been using a regular CSD, and it moves water. I'll try to get some pics, or a movie, but on a ~60 gallon, 48"x24"x12" sps frag tank, I have a 32 gallon CSD, that fills in 3-4 minutes, and emptys in like 45 seconds... a lot of surge.... It's so much surge that it can easily knock over maricultured acro colonies (you know the ones with the nice bases....