Well I'm getting my Geo's tomorrow (Friday) and have been thinking about changing my tank up a bit today. I was going to just go to Petsmart and buy some Sand but have heard some mentioning Pool Filter Sand that you can buy at home depot. Is this sand ok for Geo's? I have heard that it tends to have sharp edges and with Geo's digging so much I'm worried it may harm them. Does anyone else use this type of sand with there Geo's? I think i will go with all sand and driftwood and a few smooth rocks this time around and no caves. I would need to do this tonight if i'm going to do it at all. Right now the tank has medium sized gravel but i wanted to give the new Geo's a tank that they can really play in. I do have a pair Oblongums in the tank right now and would it be ok to leave them in the tank while I switch out the gravel for sand?