Squamosa Clam

The squamosa clam is easily distinguished from other giant clams by the widely spaced, leaf-like raised rows of scales on its shell; this is why it is called the "fluted" giant clam in English. Its mantle is usually spotted or striped in brown, gold, turquoise and blue; solid bright blue forms are rarer. In the wild it can exceed 40 cm; in the aquarium it usually stays at 20–30 cm.

Symbiotic algae in its mantle produce nutrients from light. Doing well even under moderate light compared with the maxima and crocea clams, and being able to sit on the sand without boring into rock, make it a good choice for a first clam.

Legal note: All Tridacna species are listed in CITES Appendix II; their international trade requires a permit. Only documented, preferably farm-raised (maricultured) individuals should be bought.

It lives on shallow reefs, in lagoons and on reef flats from the Red Sea and East Africa to the Central Pacific. It does not embed its shell in rock; it sits on coral rubble or sand, loosely attached by fine threads (byssus).

• Volume: at least 200 liters and a mature, stable reef aquarium at least 6 months old.
• Water: salinity 1.024–1.026 specific gravity, pH 8.1–8.4, temperature 24–27°C; calcium 400–450 mg/L, alkalinity 7–9 dKH, magnesium 1250–1350 mg/L, all stable.
• Light: moderate to strong lighting. It is usually placed on the sand or on a flat stone on the sand. A newly arrived individual is first placed in a more shaded spot and acclimated to the light over a few weeks.
• Flow: moderate, random flow; strong flow should not hit the mantle directly.
• Reef compatibility: Reef-safe; it should not be shaded by corals and should be kept out of reach of stinging corals.
• Acclimation and medication: Acclimate by the drip method for at least 1 hour; air getting trapped inside the shell during transport is harmful, so it should be moved underwater. Copper-based medications are lethal.

It gets most of its food from light; it also filters the water and makes use of fine particles and dissolved nutrients. For small individuals (under 10 cm), giving phytoplankton several times a week is beneficial. Very low nitrate and phosphate can make it harder for it to feed in the long term.

Immobile; when a shadow falls on it or it is touched, it quickly retracts its mantle and closes its shell. Small light-sensitive spots on the edge of the mantle detect an approaching shadow.

Good companions: clownfish, tangs, gobies, cardinalfish, reef-safe fish; cleaner shrimp, snails.

Avoid: fish that may pick at the mantle, such as dwarf and large angelfish, butterflyfish, some wrasses and pufferfish; large hermit crabs that climb onto the mantle.

It can be kept singly; if a second clam is added to the same aquarium, they should be placed so that the open mantles do not touch or shade each other.

It first matures as a male, then produces both eggs and sperm. It releases its gametes into the water; after a short planktonic stage the larvae settle and take up symbiotic algae. It is bred this way on farms; it is not bred in home aquariums.

• Parasitic snails: rice-grain-sized pyramidellid snails living on the edge and underside of the shell feed on the clam; check with a flashlight at night and remove them.
• Retracted mantle: a mantle that does not open fully for days, a hole opening at the base of the shell or a bad smell are signs of a serious problem.
• Bleaching: fading of the mantle is linked to changes in lighting or swings in water parameters.

It is a hermaphrodite; there is no external distinction between the sexes.