Ultra Blue Maxima Clams (Medium ~5") - WYSIWYG

Tridacna clams are stunning invertebrates that add a centerpiece of movement and color to reef aquariums. Their vibrant mantles shimmer with iridescent blues, greens, golds, and purples, while their natural filtering ability helps improve water clarity. With proper lighting, stable parameters, and occasional feeding when young, Tridacna clams can thrive for decades in a home reef.

Scientific Name & Identification

Tridacna clams (Tridacna species) are recognized by their large, fleshy mantles that extend over a sturdy shell. They contain symbiotic zooxanthellae, which provide most of their nutrition through photosynthesis. Maxima and crocea clams are smaller, rock-boring species, while derasa, squamosa, and gigas grow much larger and typically rest on sandbeds. Mantle coloration varies widely and is one of the key identifying features.

Natural Habitat

Native to the Indo-Pacific, Tridacna clams are found in shallow reef flats and lagoons, where they receive intense sunlight. Their natural placement in high-light, nutrient-rich environments guides their aquarium care needs.

Aquarium Care & Setup

Temperature: 75–82°F (24–28°C)

pH: 8.1–8.4

Salinity: 1.024–1.026

Flow: Moderate; enough to deliver nutrients and prevent detritus buildup, but not so strong that mantles retract

Lighting: High-intensity reef lighting (150–350+ PAR depending on species)

Placement:

• Maxima, Squamosa and Crocea: Prefer rockwork and may bore into it
  
• Derasa and Gigas: Do best on sandbeds with room to grow
  

Feeding Tridacna Clams

Young clams under 3 inches benefit from regular phytoplankton feedings, as their mantle surface area is not large enough to sustain them solely through photosynthesis. Mature clams rely primarily on light but still benefit from occasional phytoplankton or fine suspended foods.

Growth and Behavior

Growth depends on the species: maxima and crocea remain relatively small (6–12 inches), while derasa, squamosa, and gigas can grow to massive sizes. Tridacna clams filter feed continuously, improving water clarity as they consume plankton and particulates.

Tankmates

Tridacna clams are peaceful but can be picked at by angelfish, butterflyfish, and some wrasses. Safe companions include tangs, clownfish, gobies, cleaner shrimp, and snails.

For more information, check out our Tridacna Clam Care Guide.

Are Tridacna clams hard to keep?

They require stable parameters, very high lighting, and occasional feeding when small, but are hardy once established.

Do Tridacna clams need to be fed?

Juvenile clams under 3 inches benefit from phytoplankton feedings. Larger clams get most of their energy from light but may still benefit from supplemental feeding.

What lighting do Tridacna clams need?

High lighting (150–350+ PAR depending on species). Maxima and crocea need the most intense light.

Where should I place Tridacna clams in my tank?

Maxima, squamosa and crocea prefer rockwork, while derasa and gigas should be placed on the sandbed.

How big do Tridacna clams get?

Maxima and crocea remain relatively small (6–12 inches), while derasa, squamosa, and especially gigas can reach well over 2 feet.

Are Tridacna clams reef safe?

Yes, they are peaceful filter feeders, but should be protected from fish that may nip at their mantles.