Tridacna Clam - Crocea Clam
There are several different species of Tridacna clams available. There is the T. maxima which gets to be about 12 inches. The T. derasa which gets even bigger than the maxima. Then comes the Tridacna crocea which stays smaller, usually only growing to about 6 inches (15 cm). All of these clam species are quite colorful and eye catching. There are blue, blue-green, brown and other color varieties. T. croceas usually run anywhere from $30 to $100 dollars depending on your location. These clams are very easy to care for, provided that you have high intensity lighting over your tank.
For standard sized and shallow tanks you may be able to keep these with power compacts with multiple bulbs. For deeper tanks (those greater than 24 inches deep) you'll need HO, VHO or even better, Metal Halides. They get most of their needed nutrients from photosynthesis and the aquarium light you put over your clam tank is crucial for their well being. They are also filter feeders and will feed on dissolved nutrients in the water column. They take up ammonia and nitrates and should do ok in aquariums with normal nitrate levels (less than 20ppm).
Placing your clam is important and you don't want to be moving it around all the time. This can stress them and even lead to their demise. Find a spot and stay with it. If you have moderate lighting levels you will want to place them in a crevice in the live rock in the mid to upper regions of the tank. Tanks with higher lighting levels may be able to place them in the sand.
http://www.fishlore.com/profile-croceaclam.htm
