<a href=showthread.php?s=&postid=8283565#post8283565 target=_blank>Originally posted</a> by csammis
The Tridacnid forum will be able to give you a lot of details on what a clam that isn't getting enough light looks like.
Chiming in to say that I kept a Derasa under 130W of PC in a 10 gallon nano quite successfully. It was never more than about 12-14 inches away from the lightsource, and the water was heavily skimmed...those probably contributed to the success.