Crocea Tridacna Clam: Ideal Reef Aquarium Inhabitant

Tridacna Clams have circumnavigated the saltwater aquarium hobby for years now, however, it doesn't seem as if they have been credited with the fame they deserve. The so called "Giant Clams" are a unique family of bivalves offerring a myriad of colors, patterns and diversity, to most reef aquariums. Not only are many of these Tirdacna Clams readilly available, but the price has come down somewhat and , especially for the 1"-2" gem sized ones. The Crocea and Maxima are two of the most brilliant of all the Tridacna and Hippopus species of clams, but remain a little more expensive than their cousins.

The Crocea clam hails from the Western Pacific from Malasia, Japan, Thailand south to New Guinea and Northern Australia. As for the native people that live along the Crocea clams geographical boundaries, Tridacna clams represent a favorable and heavilly relied upon food source, since they are fairly common, easy to find and taste very sweet, much like our Native Lobster, here in New England. The saltwater aquarium trade provides a much needed sourse of income for the locals as well. Many marine aquarium enthusiasts, retail outlets, online venues, and wholesalers, are in the market to obtain the so-called Giant Clams.

Crocea clams prefer intense light not only to bring out their vibrant colors but in order to survive as well. The reason for this is that any symbiotic animal, like the Corcea clam, lives in a symbiotic relationship with single celled organisms called zooxanthellae. These algae live primarilly in the syphonal an lateral mantle to a lesser degree. The clams provide their zooxanthellae with a home while the zooxanthellae returns the favor affording its host with beneficial nutrients, like lipids, glucose and carbohydrates. The outter syphonal mantle reminds me of a human fingerprint. To a clam, no two mantles are alike and represents its own sort of unique identification.

Representing the smallest member of the Tridacna clam family, Crocea clams will attain 4-6 inches in diameter and weigh somewhere in the vicinity of a few pounds. One of its relatives, the Gigas clam, can reach 3 feet or more in diameter and weigh in at 500 pounds or more.

For the most part, a Tridacna or Hippopus Giant Clam can be differentiated from one another based on byssus opening, whether the shell has scutes(ridges or scales), symmetry of the shell and to a much lesser degree, mantle composition and color. In the wild, the Crocea is a boring clam, much like another close cousin of it, the maxima clam. This means that the grow on a hard surface such as a rock or coral formation and as they grow, will continually move around in one place like a drill. Eventually the clam will move deeper and become encrusted, for safety, inside the confines of its solid exterior. As juveniles, clams contain byssus threads that are produced and attach Tridacna clams to any surface. These threads eventually disappear once a clam attains a certain weight, or has encrusted itself into a hard surface. these threads act like a glue or suction to adhere the clam from drifting from a favorable location, stability with respect to water current and turbulence and also provide protection to some degree.

Feeding of Tridacna has come with heated debate in past years. The reason for this is their were two schools of though. One school believed that juvenile Tridacna clams needed to be fed very small phytoplankton that could be digested easilly without initiating a "coughing reflex" , a natural reaction used to spit the larger food out. Without optimal nano and phytoplankton, this school of though condoned clams would ultimately die of starvation.

The second school of thought insists that any clam, regardless of its size, once it develops zooxanthellae in its mantle, did not need to rely on nano and phytoplankton for survival, as the clams host zooxanthellae could provide all necessary nutrients. Moreover, clams are filter feeders. Because of this, they are able to take in water from its surrounding and filter out dissolved organics, nitrates, phosphates and small particulate matter to satisfy their dietary needs.

As for maintaining one of these beautiful Crocea, or other Tridacna clam species in a marine aquarium environment, ensure you have a healthy individual from the retail outlet is number one. Providing proper light, stable water parameters with elevated calcium and alkalinity levels for shell growth, and a strees free environment will help greatly in your overall success in caring and enjoying these beautiful animals as close as your living room.


"Giant Clams" by Daniel Knop pp.21