I believe they are one of the faster growers. I had one that added about 4-6" of shell in about 6 months. If you place them in the sand, I would recommend you place a flat rock or something under ther sand, under the clam. I placed mine in the sand to see if it liked the spot and before I knew it, it had attached itself to the glass bottom. The clam was later lost when I tried to move the clam while cleaning the glass
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,