I put mine in sand and I only had issues with it floating up when I get too close with a siphon hose. With that ecoC I wouldnt expect it to float as long as it was flooded slowly, and heck if it did with a 3g just reach down and poke it back in. I pulled up a huge clump with runners one day, it went all the way through the tube to the bucket, I just replanted and that patch has shown no ill effects. I cannot offer advice on when to flood though as I have never done a DSM. Good luck!