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Derasa clams are the largest commonly-kept Tridacna species - reaching 24 inches in captivity. More tolerant of moderate lighting than Maxima or Crocea, making them a better entry-level giant clam choice. Color ranges from gold to brown to subtle green with characteristic ridged shell pattern.
Native range: Indo-Pacific reefs. Most US trade specimens come through marine wholesale suppliers in Indonesia, the Philippines, Hawaii, and the Caribbean. Wild collection remains the primary sourcing method for the majority of marine inverts - few are captive-bred at commercial scale. Quality of acclimation at the wholesale/retail stage is the biggest single predictor of long-term survival in home aquaria.
Tank size: 75 gallons. Parameters: temperature 76-82°F, salinity 1.024-1.026, plus the standard reef tank requirements - stable calcium 420-440 ppm, alkalinity 8-10 dKH, magnesium 1300-1400 ppm, nitrate under 25 ppm, phosphate under 0.05 ppm. The species requires conditions consistent with a healthy reef tank rather than nutrient-stripped sterile water - well-established systems with diverse microfauna and biofilm typically support these inverts better than newly-cycled tanks.
Lighting: depends on species. Photosynthetic inverts (clams, anemone-symbiotic species) require high-PAR reef LED lighting. Filter-feeders (worms, scallops) prefer moderate lighting and benefit from particulate-rich water. Flow: moderate, indirect flow works for most inverts - direct high-velocity flow stresses or damages soft-bodied species.
Acclimation: drip acclimate over 2-4 hours for hardy species, 4-8 hours for sensitive species (Linckia stars, sea hares, demanding nudibranchs). Never expose inverts to air during transfer - capture in a bowl underwater and transfer wet.
Derasa Clam diet: Photosynthetic + filter feeding. Feeding strategy depends on dietary type. Algae eaters require established tanks with biofilm and microalgae growth - new tanks lack the algal base they need. Carnivore inverts (starfish, some snails) need targeted meaty feedings 2-3x weekly. Filter feeders (clams, worms, scallops) need phytoplankton in the water column. Photosynthetic species need adequate lighting plus supplemental amino acid or coral food dosing.
Safe: Most reef-safe fish, peaceful corals.
Avoid: Mantle-nippers, Pyramidellid snails.
Same as Maxima - mass spawning, rarely captive bred.
Slower expansion in too-low lighting; calcium deficiency causes shell pitting; pyramidellid snail infestation.
Yes among Tridacna species - more tolerant of moderate lighting and parameter ranges than Maxima or Crocea.
Wild specimens reach 24 inches. Captive clams typically reach 18 inches over 10+ years.
Yes - unlike Maxima/Crocea (which need rock for byssal attachment), Derasa clams sit happily on sand bottoms.
4-6" specimens $80-200. Larger specimens $250-600+.
Fast Aquatics vendors ship marine inverts overnight to all 50 US states with carrier-tracked Buyer Protection.
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