and the tank is a 500g 8x4x25" with a 100g sump under there and a reeflo hammerhead moving some serious water. the rays seem to be enjoying themselves, takes some getting used to sand since they were barebottom for the last 3 years, but no serious irritation that ive noticed. as far as scaping, the rays rearranged it anyways so ill let them do their own thing. they moved some very large rocks easily over 20lbs and all the sand from the front of the tank to the middle to make a raised almost sand bar they play on. its amazing just the sheer mass of these guys, my 500g is looking awefully small now lol. (good excuse to go bigger maybe?)