Genus = Tridacna
Species = gigas
Common name= Gigas clam
This big beauty belongs to Kevin of www.aquaticdreams.com and measures 22"
Size and growth rate
T. gigas is truly the Giant Clam of legend. This species can grow to over 4 feet in length and weigh up to 440 pounds. Gigas are the fastest growing of all the giant clams. These clams have been reported to grow as little as 4cm and as much as 12cm per year. To my knowledge the Waikiki Aquarium houses the largest Giga's in captivity, from my understanding I think it is about 34" long.
Location and geographic range
This gentle giant can be found in shallow lagoons and muddy grass flats, and even as deep as 15 meters. It is very common for these clams to be exposed to air during low tides due to their tendency to live in such shallow waters. Gigas range from Thailand, to western Australia, to Micronesia, and northward to the southern islands of Japan.
Attachment to substrate
As juveniles, T. gigas uses their a byssal organ that secretes the sticky threads that will attach it to the substrate. This helps keep the clam from being swept away. In time this organ atrophies, the byssal opening grows shut with shell, and the large size of the animal helps keeps it in place.
Lighting and flow requirements
Gigas are probably the least light demanding of all the giant clams, even though they still require high end light. They will probably be OK with VHO or compact fluorescent lights but I recommend metal halide or T5 with individual reflectors. Giant clams are found on reefs that usually have SPS corals, flow should be moderate to high. Just be sure that the mantle isn't being held over un naturally because of too much flow.
The Gigas clams are most commonly brown, tan or green. I have seen pictures of Gigas clams that are blue, purple and even have black.
Giant clams are found among the reefs of the world and are compatible with most reef safe animals. Although there are some reef safe fish that are not clam safe. These include: Angelfish, some Wrasses, Blennie's, Eels, and some shrimp.
Conclusion and comments.
Gigas are fairly uncommon to the aquarium industry. They are being farmed but due to over fishing in their natural habitat the farms are sending most of the farmed Gigas back to reseed the oceans. There is a small percentage of them that do make to our LFS's so don't lose hope.
It is my personal opinion that if you intend to keep a Tridacna gigas you should have an aquarium of 100 gallons or larger. They can be kept in smaller tanks but they rapidly outgrow them.