I added a small Derasa to my tank a couple of weeks ago and have been trying differnet locations to see where he would be happy and attach. It has been bulldozed many times by turbo snails and has landed right next to a small cabbage coral and has now attached itself to the rock. When it opens it's mantle touches the cabbage. It seems to be happy there and stays open but does anyone see any problems with this close location to a coral? Will the clam detach itself if it has any problems?

Derasa are one of those clams that as it matures, and gets heavier, will loose its need and therefore capability of byssus activities. Basically, due to the sheer weight of the clam, it eventually does NOT need to use byssal threads to attach to a substrate.

They are also, for the most part, happier on the sand bed rather than on the rockwork. If you look to see where they are found in the wild, you will see why. They are not boring clams, who associate with rock plateaus etc. but are more often found in sand in turbid areas. This is also why they are not as brightly colored as other tridacnid clams. IF yours is brighter in color, I'd place it higher in the system (dependant on lighting. They do NOT like to be close to MH or very bright lighting). If it is browner, greener, or otherwise more 'earthy' in color, place them directly in the sand.

With that said, as a juvenile, it SHOULD have some attachment. Not neccessarily in your rocks, but possibly in the sand. Take a small, flat piece of LR and put it on the sand. Put the clam on top. It should take to the rock. Then simply bury the lil' rock in the sand up to the base of the shell of the clam to hide it. This allows the clam to protect the byssal port from predation from worms, snails etc.

I'd not want my clam mantles touching any corals. Not only is it subjected to the coral, but is most likely shaded by it too. You may note faint loss in color in that area.

If you can move it, I'd do it.

Dave