Tridacna Derasa vs Maxima Comparison: Clam Care Differences

The first giant clam a Singapore reefer encounters is almost always a small Tridacna maxima imported through Iwarna or Reef Depot, and within two years the conversation shifts to whether a larger derasa would have been wiser. This tridacna derasa vs maxima comparison from Gensou Aquascaping at 5 Everton Park draws on observations from seven client reefs housing one or both species over the past five years. The two clams look superficially similar but behave differently under captive conditions, and choosing the wrong one for your tank setup costs real money.

Natural History and Origins

Tridacna maxima is the colourful, reef-edge specialist found across the Indo-Pacific at shallow depths from 2 to 15 metres. Its mantle carries the spectacular blue, gold and teal patterns that drive collector demand. Tridacna derasa is a larger, sand-dwelling species inhabiting slightly deeper lagoon floors; mantles are handsome but generally less patterned. Both host symbiotic zooxanthellae and rely on photosynthesis for most of their nutrition.

Size and Tank Footprint Considerations

Maxima typically tops out at 25 to 35 cm in captivity; imports arrive at 5 to 12 cm. Derasa grows substantially larger, reaching 45 to 60 cm over a decade and needing a footprint to match. For a 60 cm cube, only maxima is appropriate. For 120 cm and larger reefs, derasa becomes a sensible centrepiece. Factor ultimate size into nano reef aquascaping layout planning; a 30 cm clam on a small sand bed dominates visually and physically.

Lighting Demands

Maxima is the more light-hungry of the two. Placement near the top of the rockscape under 250 to 350 PAR is typical; under-lit maximas within six months show pale mantles and stalled growth. Derasa, adapted to deeper lagoon habitats, tolerates significantly lower light — 150 to 250 PAR at the sand bed is adequate. Our nano reef lighting PAR requirements guide maps fixture selection against target PAR zones. Derasa under a maxima-grade light will bleach from excessive PAR; maxima at substrate level will slowly die from insufficient light.

Placement Logic on Rockwork Versus Sand

Maxima is a rockwork clam. It attaches via byssal threads to hard substrate and belongs mid-to-high on the reefscape. Placing maxima on sand is a common beginner mistake; it cannot anchor and will topple during flow cycles. Derasa, by contrast, sits flat on coarse sand or rubble and does not form significant byssal attachments. The two species occupy distinctly different niches in the aquascape and cannot be swapped casually.

Water Parameter Stability

Both clams demand stable calcium (420 to 440 ppm), alkalinity (8 to 9 dKH), and magnesium (1300 to 1400 ppm). Maxima is marginally more sensitive to alkalinity swings; a jump from 7 to 10 dKH in 48 hours will stress maxima faster than derasa. Our balling method reef dosing guide covers the protocols that keep parameters steady. Both respond poorly to elevated phosphate above 0.1 ppm and both need steady nitrate around 5 to 10 ppm rather than stripped bare.

Feeding Requirements

Contrary to older advice, both species benefit from supplementary phytoplankton and targeted amino-acid dosing during the first six months post-import. Reef Nutrition’s Phyto Feast at 1 ml per 100 litres twice weekly is our standard approach. Larger specimens derive more nutrition from photosynthesis and require less targeted feeding; small imports under 8 cm benefit from weekly phytoplankton during the acclimation period.

Import Channels and Singapore Pricing

Both species enter Singapore through CITES-permitted farmed stock, predominantly from Vietnam and the Solomon Islands. Pasir Ris Farmway vendors and Reef Depot are the primary retail points. Maxima at 8 to 10 cm retails for $150 to $280 depending on mantle colouration; derasa at 10 to 15 cm sits at $120 to $220. Our Pasir Ris Farmway vendor guide identifies which vendors consistently source healthy, quarantined clam stock.

Pest and Health Watch

Both species are vulnerable to pyramidellid snails, which appear as tiny parasitic white dots along the mantle margin and reproduce rapidly if not addressed. Quarantine every new clam in a dedicated tank for two weeks, inspecting with a magnifier at dawn when the snails are active. Failure to spot an infestation early can kill a $200 clam within three weeks.

Flow Tolerance

Maxima tolerates moderate-to-strong flow and in fact benefits from intermittent gust patterns that mimic surge zones. Derasa prefers more moderate, less turbulent flow. A tank with a single strong gyre pump suits maxima on the upper reef; derasa on the sand wants calmer conditions.

Which Clam for Which Reefer

For a nano or mid-sized reef under 200 litres with strong lighting, maxima is the natural choice and delivers the mantle colour most collectors seek. For a larger reef over 300 litres with a generous sand footprint and lower overall PAR, derasa is the pragmatic centrepiece that grows steadily into a remarkable display. Either way, plan for long-term commitment — these clams live decades when conditions are right, and our maxima clam care guide and derasa clam care guide cover species-specific husbandry once you have chosen.

Related Reading

• Maxima Clam Care Guide Reef
• Derasa Clam Care Guide Reef
• Nano Reef Lighting PAR Requirements
• Balling Method Reef Dosing Guide
• Pasir Ris Farmway Vendor Guide