Step 2. Cover frame in black pond foam. The foam I used is for securing rocks in outdoor ponds. I bought my can at the local hardware store for like $6.00. I buried the racks in about 2 inches worth of old sand I had. This reduces the amount of foam needed, saving cost and reducing the buoyance. The foam expands when first applied. After I applied some, I came back and smushed the foam down. It kind of pops almost. I spread it around with a paint stick (I think). It puffs up some again and leave a nice lumpy texture. Gloves are a must. It is very sticky stuff.