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Crocea Clam - Tridacna croceaCrocea ~ Crocus Clam ~ Boring Giant Clam

Family: Cardiidae

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Tridacna croceaPhoto © Animal-World: Courtesy David Brough

     Tridacna crocea, the Crocea Clams, are some of the most colorful members of the giant clams!

     Saltwater aquariums fascinate us because of the unique personalities and antics of their inhabitants, so perhaps a giant clam just sitting there seems a rather unlikely choice. But after one look at these beautiful creatures it is easy to understand why enthusiasts are eager to include them in their tanks. The Crocea Clam is a favorite. It is the most colorful of the Tridacna genus and could arguably be said to be the most popular, vying only with the Maxima Clam for the honor.

     Tridacna Crocea are beautiful giant clams with a variety of patterns and color mixtures. They have fascinating designs in blues, purples, yellows, greens, browns, golds, and oranges. The mantle is usually decorated with iridescent blue, yellow, or green blotches, spots or lines. With its maximum length being only 6 to 9 inches (15.2 to 22.9 cm), T. crocea is also the smallest of the Tridacna clams.

     Though often simply referred to as a 'Crocea', the Crocea Clam is also known by a number of common names including Crocus Clam and the Saffron Colored Giant clam. Because it is a Boring Clam, burrowing into boulders and coral heads, it is also called the Boring Giant Clam. With some specimens being intensely colored and strongly patterned, you will also find references to them in the aquarium industry under such names as Ultra Crocea, Ultra Grade Crocea, Super Crocea, and Electric Blue Crocea.

Scientific name
   Tridacna crocea

Distribution / Background

     The Crocea Clam is found in the Indo-West Pacific. Its distribution in the wild ranges from Thailand to New Caledonia. Tridacna crocea was first described by Lamarck in 1819.
     T. crocea's are usually found in the shallow areas near the shore or on the upper-most areas of the reef. These clam's are known as the Boring Clam because with the contraction and relaxation of their byssal muscles, they burrow into boulders and coral heads. Once burrowed, they use their byssal threads to hold themselves in place. Usually only the top edges of the shell and mantle are visible.

Status

     The Tridacna crocea is listed on the IUCN Red List as LC - Least Concern.

Description

Photo  © Animal-World

     Some characteristics of Tridacna crocea:

• large and wide byssus gland opening
• smooth shell with closely placed scutes
• scutes are on the upper portion of the shell only
• the inhalant siphon have very small and fine tentacles
• clams from aquaculture systems will have scutes along the entire shell since they haven't ground them down as a result of burrowing
• shells have a symmetrical shape

Photo by Harbor Aquatics

     The picture to the right clearly shows the scutes on the upper portion of the shell only.

   The lower scutes have been worn away by the clam's burrowing habits.

     The image to the left clearly shows the tentacles on the inhalant siphon of the T. crocea.

     When giant clams are juveniles, it can be oftentimes be difficult to tell them apart. The Crocea Clam is sometimes confused with both the Maxima Clam T. maxima and the Giant Clam or Gigas Clam T. gigas.

     Comparing Crocea Clams to other species of Giant Clams:

• Maxima Clam:
     Crocea Clams are often confused with the Maxima Clam T. maxima. This is because the color patterns of these two clams is similar. Which clam is which can be determined by their shells, which are much different.
       The Maxima Clams usually have an elongated shell. The scutes of T. maxima are also more pronounced and they cover most of the shell. Their difference may also be determined by the byssus gland, which on the Crocea Clam is very long and wide.
• Giant Clam:
     When the Giant Clam T. gigas are young, they are also sometimes confused with the Crocea Clam. The differences are in the coloring of each clam. Also, the shell of the T. gigas is generally missing scutes (or they are very sparse) and its ribs are more pronounced.

Difficulty of Care

     The Crocea Clam is not only beautiful, but can be a good choice for a beginning saltwater enthusiast. Both the Crocea Clam and the Maxima Clam are fairly tolerant of strong water motion and relatively strong fluctuations in water parameters, more so than some of the other Tridacna clams.

Foods / Feeding

     It is generally believed that giant clams do not require feeding in the aquarium. Most clams fulfill their nutritional requirements by filter feeding and absorbing dissolved organic compounds from the water. The Tridacna clams have gone even further than this, using zooxanthellae to manufacture food for themselves.
    The Tridacna clams receive the majority of their nutrition from their zooxanthellae. Whether additional feeding is required is still debated. Some hobbyists believe they should be fed, going on the assumption that they are filter feeders like other clams. If you wish to feed your clam, it is suggested that they be fed micro-foods designed for filter feeders, especially when small. A yeast-based suspension is one suggestion, unless the tank has other fish and corals that are regularly being fed, or you can offer other micro-foods such as phytoplankton or commercially prepared micro-foods like 'marine snow' or 'reef snow'.
   Basic nutrients in the aquarium that giant clams need are calcium, strontium, iodine, and possibly a minute amount of nitrate.

• Calcium: Calcium is the main building block for clams and should be present in the water at levels of at least 280 mg/L for growth to occur. More rapid, natural growth is seen when calcium is in the range of 400-480 mg/L.
• Strontium: Strontium is incorporated in the shell along with calcium and should also be provided for optimum growth.
• Iodine: The addition of iodine to the aquarium will also enhance growth and color in giant clams.
• Nitrate: They require some nitrogen for proper growth. Nitrate can be added if levels are extremely low, but be careful as nitrates should never exceed 2 mg/L.

     For more information about the feeding process of Crocea Clams see What Do Clams Eat.

Aquarium Care

Photo by Harbor Aquatics

     If a healthy clam is obtained and proper light provided, these clams are relatively easy to keep. With proper lighting and careful attention, Crocea Clams require require little else in the way of care. It is important to make sure they are not being irritated, not being fed upon by other organisms, and good water quality must be maintained.

• Crocea Clams are sensitive to being handled so avoid it if at all possible. Because these clams burrow into rock and rely heavily on their byssal threads for attachment, they will eventually bore into a substrate or other substance on which they are placed. Damage that could be done when messing around with an attached clam.
• Keep a watch for predators as this clam can be easy prey with its large and wide byssus gland opening.
• Crocea Clams can handle strong water motion and relatively strong fluctuations in water parameters, but you really don't want your water parameters to fluctuate too much!
  

Aquarium Parameters

     Crocea Clams can be kept in a reef environment with live rock. They should be placed on live rock or some other solid material they can attach to. Make sure if placing them in a depression of live rock that they can still fully open their shell. They can handle strong water motion and relatively strong fluctuations in water parameters, but high pH and high temperatures can cause problems.

• Lighting:   Coming from shallow waters in the wild, these clams will need intense lighting. If you plan to keep these clams under fluorescent lighting, keep them close to the top of the tank, and the lights.
     If the clam is predominately brown and showing little of it's normal coloration and patterning, it should be placed lower in your tank away from strong lighting. The brown coloration is the clam's zooxanthellae showing and is probably due to the clam losing it's protective coloration during it's long trip.
• Temperature: Upper 70 ° F. (mid 20 ° C.). Do not let the aquarium exceed 82 ° F.
• Salinity / Specific Gravity: 1.024. Salinity is also important, too high or low a salinity can cause the death of a clam. Try to keep specific gravity between 1.023 and 1.025.
• pH: 8.3. Do not let the aquarium exceed a pH above 8.4.
• Hardness: Maintain a dkh of 7.9.
• Water Movement: Crocea Clams can handle strong water motion, however high currents should not be a constant condition.

For more in depth information on caring for Crocea Clams see, Caring For Tridacnid Clams

Compatibility and Social Behaviors:

     Clams are very stationary and peaceful, they are not aggressive towards other aquarium inhabitants. Though they have the ability to shut completely, they do need protection from anemones and some corals. They should not be kept near any stinging cell creatures and must be kept away from any sweeper tentacles. Anemones need to be watched, as they can move close to a clam and sting or eat it.
     Be cautious with other tank inhabitants as well, those that may pick at the clam or eat its mantle, such as Trigger Fish and Puffers. Blennies, Butterfly Fish, Clown Gobies, Angelfish and shrimp may disturb Tridacna clams.

Breeding and Reproduction

     Crocea Clams have been propogated in captivity, and the demand from aquarists has raised interest in producing colorful varieties of all the species.

     For detailed information of tridacnid propogation, see Giant Clam Breeding and Reproduction

Potential Problems

     Keep a watch out for predators! The Crocea Clam can be easy prey with it's large and wide byssus gland opening. They are also quite sensitive to chemicals or toxic substances dissolved in the water, so be sure to maintain good water quality. As mentioned under aquarium care and aquarium parameters above, high pH, high salinity, and high temperatures can also cause problems.

    For in depth information on potential Tridacna clam problems, see: Tridacnid Clams: Friends, Enemies & Ailments

Availability

     Clams obtained from aquaculture systems are readily available and are very hardy in reef aquariums.

     Because the Crocea Clams burrows into the rock and attaches itself with their byssal threads, collecting them from the wild is more difficult and the chances of receiving a damaged clam are greater. Once the byssus gland is damaged, the clam doesn't usually live long. This is most likely due to bacterial infections though, and not the damage itself. You will have a much better chance of keeping a wild collected clam if you receive it still attached to a rock.

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