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Introduction to Clams |
Tridacnid clams are the most commonly kept clams in the reef aquarium. This is the family of clams the include the largest clams in the ocean and most get moderately large (6") to very large (3' or more). Coloration varies from species to species, but most are very attractively colored. They all survive off symbiotic algae called zooxanthellae that lives within their tissues and require no feeding. Related bivalves sometimes sold at the LFS include flame scallops and oysters of various types. These are all filter feeders and are generally not very suitable for the reef tank.
The picture above shows a T. squamosa on the left, and two T. maxima tridacnid clams. The middle picture is a T. derasa. The picture on the right is a T. gigas, the giant killer clam of folk lore.
All tridacnid clams require at least moderate lighting and some require very intense lighting. Ensure that tank has sufficient lighting to support the type of clam you are thinking about buying. If lighting is insufficient, the clam may show very high mantle extension. Although this may look like a happy clam, in fact it can indicate that the clam is trying to extend its mantle for maximum light gathering due to inadequate lighting conditions. Clams in the wild do not show much mantle extension.
Guidelines to buying tridacnid clams
Chose specimens that respond to a shadow or touch. The clams should shut it's shell with some amount of force.
Inspect the mantle. It should extend past the edge of the shell and not have tears, holes or obvious damage to it.
Look for gapping. This is when the clam opens it's shell very wide with little or no mantle extension. The intake siphon opening is frequently widely distended as well. This is frequently associated with low response to stimuli. Gapping is a sign of a sick clam that should not be purchased. Unlike some marine animals, sick clams almost never recover even when put in optimum conditions.
Ensure you have the lighting to support the type of clam you are contemplating buying.
Keep in mind that some types of tridacnid clams can get large fairly quickly, especially T. gigas and T. derasa. A T. derasa calm can grow from a length of 2" to 8" in just 12 to 18 months.
When placing the clam in the aquarium, there are some general guidelines to follow
Position the clam where it cannot be stung by any of its neighbors. Clams are not very tolerant of bothersome neighbors.
Ensure you place the clam on a suitable substrate. If it is positioned up on the live rock, it should be kept in place by rocks or similar or the clam may 'jump' from its position using it's foot and tumble down the live rock.
No clams like a lot of water current, although some are more tolerant of this than others.
Watch the clam after introduction to ensure it is not being molested by any of the fish or invertebrate inhabitants. A new clam will frequently have tasty stuff on its shell that is new to the tank and so it is not uncommon for fish to show an interest in it when first introduced and should not be a cause for concern as long as they do not bite at and tear the mantle.
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The picture above shows the new white growth area at the edge of the mantle which is typical of a healthy fast growing clam.
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Clams will occasionally expel a brown or green stringy looking material from their exhalant siphon as shown in the picture above. This is not a cause for concern and appears to be the way in which the clam expels excess zooxanthellae or possibly other waste products.
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Clams will sometimes spawn in the reef aquarium. The photos above show two Derasa clams spawing in my reef tank. The two clams can be seen in the picture on the right. Spawning in a reef tank does not result in any viable baby clams being produced.
See acclimation procedure for further information on introducing Clams and other specimens to the tank.
Further Reading:
Getting
Up-To-Date on Zooxanthellae
By Eric Borneman
Variations
in tridacnid shell formation
By Daniel Knop
Reef
Tank Design for Giant Clam Lovers
By
Daniel Knop
How
to Choose Healthy Giant Clams at the Aquarium Store
By
Daniel Knop
Placing
Giant Clams in the Reef Tank
By
Daniel Knop
Gamete
Release by Giant Clams in Aquaria
By
Daniel Knop
Fish
“Bullies” in the Giant Clam Tank
By
Daniel Knop
Cunning
and Malicious: Parasites and Predators of Giant Clams
By
Daniel Knop