Giant clams are some of the most colourful and wonderfully patterned creatures in the ocean. For this reason they are often quite sought after by aquarists. There are seven species of Tridacna, and two species of Hippopus. The most common in the aquarium trade in Australia are T. squamosa and T. maxima. They are reasonably light demanding creatures (generally - notable exception being T. tevora).
Clams are comprised of two shells, a mantle, the byssus or foot, and a number of organs hidden inside the mantle. On the mantle above the byssal opening is the inhalent siphon, the larger hole on the body. The other hole in the mantle is the exhalent siphon, a protruding tube-like extrusion in the mantle.
In side the inhalent siphon, a clam possesses gills, an esophagus, a mouth, a stomach - which are used to breathe and eat. Other organs include two kidneys, and incredibly both male and female gonads when sexually mature. Significant other body parts are muscles for closing and opening of the shell (adductor muscles) and a foot for attaching the clams to rocks. I nterestingly enough, when eaten it is the adductor muscle which is eaten.
Tridacnid clams are hermatypic, possessing symbiotic zooxanthellae algae in their mantle tissue. The algae are not in the cells of clams like they are with corals - they live in a special symbiot channel system that extends from the stomach to the mantle, almost like a circulatory system for the algae.
Disease / Predators / Parasites
Most common parasite as the pyramid snail, these are nasty creatures that prey on clams. They are the size of the grain of rice. Common reaction is that the clam will not open.
Care and Feeding
- Select specimens that respond to shadow or touch. Clams that retract slowly are usually unhealthy.
- A clam should not be gaping - essentially opening the shell very wide with little mantle extension of the edge of the shell, or the inhalent siphon being far too open
- Quarantine all new specimen if at all possible! They can come in with disease, parasites and even organisms that can harm other tank inhabitants (their shells are like live rock)
- Ensure you have the lighting and space to support the species of clam.
- Position the clams where it cannot be disturbed by its neighbours. Whilst in some cases inhabitants such as anemones can brush up against clams with no obvious signs, they can turn aggressive towards the clam and have disastrous effect.
- They prefer to be placed with their intake siphon the same or lower than their outlet siphon
- Clams prefer lower current areas in the tank, however most are tolerant to higher currents.
- Phytoplankton, A Necessity For Clams - by Ronald Shimek
- A Look at "Mysterious Clam Deaths" by James Fatherree - Advanced Aquarist's Online Magazine
- Feeding Clams by Daniel Knop - Reefs.org
- Removing Clams from Water by Daniel Knop - Reefs.org
- Clam with Broken Hinge Ligament by Daniel Knop - Reefs.org
- Troubles With Tridacnids: A Look At Two Common Problems by James Fatherree - Reefkeeping Magazine
- Tridacna Clams for the Home Aquarium by J. Charles Delbeek - SeaScope
- How Much Light?! Analyses of Selected Shallow Water Invertebrates' Light Requirements by Dana Riddle - Advanced Aquarist's Online Magazine
- Sample chapter on Calfos book on Wet Web Media
- Identifying the Tridacna Clams by James Fatherree - Reefkeeping Magazine
What lighting do I need for a clam?
Do I need to feed my clam?
It is recommended that you feed clams. Clams eat phytoplankton and particulate matter from the water column, but are very specific about size. Cleaning the glass can feed them. A common recommendation is to add yeast to DIY food mix for them to feed on.
How do I get my clam off the rock?
Never try to tear the clam from the rock, this can tear the byssus and lead to death of the clam. Cut the byssal threads (the tiny threads extending from the foot) with a sharp blade close to the rock surface, taking care not to cut the foot itself. Its best not to do this at all, try to move the rock itself if necessary. A week after the clam has moved it should be reattached to the rock in the new position.