Crocea Clam (Tridacna crocea)
Tridacna crocea are beautiful clams oftentimes displaying a variety of colorations with intricate patterns. These clams are also referred to as Crocea Clam, Boring Clam or Crocus Clam, and are the smallest of all Tridacna spp., reaching a maximum size of 6″ in the wild. The Crocea Clam can penetrate through limestone substrates by releasing an acid to break down the carbonate in the stone. It uses the ridges of its thick shell to dig into the rock by opening and closing quickly through the use of its large byssal muscle, giving the clam the common name “boring clam.” This burrowing behavior helps to protect it from predators such as sea stars, along with Angelfishes, Butterflyfishes, and other reef dwelling species that consume bivalves.
In the wild, the Crocea Clams often live together in great congregations, and can display a variety of colorations and patterns comprised mostly of purple, green brown, and blue with beige or orange spots. Vibrant blue or green Crocea Clams as well as ones consisting primarily of gold normally demand a higher price and are considered Electric, Ultra Colored, or Super Colored.
Tridacna crocea are found throughout the Indo-Pacific and Western Pacific oceans, and a vast majority of these clams entering the aquarium trade are wild harvested and exported from Vietnam. They can be identified by having a relatively smooth shell that is thick and heavy, and is much taller than T. maxima, which it can closely resemble in the appearance of the mantle. Like some other members of its genus, T. crocea attach to hard substrate or rockwork with thread like appendages called byssal filaments, and can eventually burrow or bore into porous substrate or rockwork in the home aquarium.
Crocea clams will arrive either unattached or attached to a small piece of rock or substrate. They will normally attach to a solid surface within a few days of being introduced into the aquarium, so keep in mind that their first placement should be considered permanent. Never forcibly remove an attached clam from the substrate or rockwork, as lethal damage to their foot and other tissue will be inevitable. As a last resort, to remove a clam from a hard surface gently cut each byssal thread with a razor blade as close to the attachment point of the rock or solid surface, making sure not to slice or damage any tissue.
Info from http://www.liveaquaria.com/
Pic from http://www.aquariumdomain.com/