ORA Derasa Clam

Quick facts

Identity

Also known as

Southern giant clam; Smooth giant clam; Sand clam

Synonyms

Tridacna cumingii

Environment

Saltwater

Native to

Australia, Papua New Guinea, Indonesia, Philippines, Fiji, Tonga, Palau, Solomon Islands, Vietnam

Habitat

Outer reef slopes of the Indo-West Pacific, typically at 4-10 m depth on sand or coral rubble, in areas of strong wave energy and bright light.

Sourcing

Both

Conservation

Vulnerable

Care

Care level

Moderate

Temperament

Peaceful

Adult size

2 – 20 in (5.1 – 51 cm)

Lifespan

15 – 40 yrs

Min tank

40 gal (151 L)

Growth rate

Fast

Placement

Bottom

Water

Temperature

75 – 81 °F (24 – 27 °C)

pH

8.1 – 8.4

dKH

8 – 12 dKH

Salinity

1.023 – 1.025 SG

Flow

Moderate

Behavior & compatibility

Social

Solitary

Aggression to own kind

Low

Active

Daytime

Reef safe

Yes

Invert safe

Yes

Shrimp safe

Yes

Clean-up role

Filter feeding

Population boom risk

Low

Feeding & breeding

Diet

Photosynthetic

Foods

Phytoplankton, Zooplankton

Breeding type

Broadcast spawner

Breeding difficulty

Not bred in captivity

Sexing

Simultaneous hermaphrodite; sex cannot be determined externally.

Target feeding

Beneficial

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Care guide

Overview

ORA-raised specimens of Tridacna derasa show orange-yellow mantle tissue broken by dark stripes and a fine blue outer rim. Among the largest giant clams, this species can approach 16 inches and is considered the most forgiving to keep, tolerating moderate reef lighting and settling directly on open sandbed rather than wedging into rock.

Care

Derasa clams are among the easiest giant clams to keep, tolerating moderate reef lighting better than maxima or crocea clams. They should rest on open sandbed rather than being wedged into rockwork, since adults typically lose their byssal attachment and simply sit under their own weight. Stable, elevated calcium, alkalinity, and magnesium are essential since this is a fast-growing species that draws heavily on all three. New arrivals do best acclimated to lower light for a week or two before being moved to full intensity.

Feeding

Most nutrition comes from photosynthetic zooxanthellae housed in the mantle tissue, so strong full-spectrum lighting matters more than direct feeding for adults. Specimens under about 4 inches benefit from regular dosing of phytoplankton or a fine reef food a few times weekly to supplement filter feeding. Once a clam reaches a larger size it generally needs no additional feeding and relies on light and ambient dissolved nutrients.

Tank mates

Best kept with peaceful reef fish and corals that will not sting or shade it, since sweeper tentacles from nearby LPS or aggressive corals can damage the exposed mantle. Avoid triggerfish, puffers, and certain wrasses known to nip at clam mantles, along with predatory crabs and shrimp. Pyramidellid snails are a persistent threat and should be checked for during acclimation and periodically afterward.

Breeding

Reproduction in home aquaria is essentially unknown, as spawning requires precise environmental triggers and coordinated release of gametes best managed in aquaculture facilities. Most specimens in the trade are produced by commercial hatcheries such as ORA rather than bred by hobbyists. Home aquarists should not expect or attempt to breed this species.

Health

Watch for gaping, a retracted mantle, or repeated slipping off its perch, which can indicate stress, poor water quality, or insufficient light. Pyramidellid snails are the most common parasite, feeding on the clam at night and sometimes going unnoticed until a population builds up. Mantle nipping from fish or invertebrates can leave the tissue vulnerable to infection if damage is severe or repeated.

Sources

1. Derasa clam care: tank size, temperature and tankmates · TankBud
2. Derasa Clam Invertebrate Care Guide | Top Shelf Aquatics
3. ORA Derasa Clam | Captive Bred Tridacna Clams | AlgaeBarn
4. Aquacultured Derasa Clam – LiveAquaria

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