01.10.2026

Tridacna Maxima, Crocea or Derasa: Which Clam Fits Your Reef?

A Tridacna clam's patterned mantle can become a focal point in a reef aquarium. Choosing one involves more than colour: light at the intended location, secure support and room for its adult size all matter. This comparison helps you weigh up Tridacna maxima, Tridacna crocea and Tridacna derasa. Find the specimens currently offered in our Tridacna clam selection.

Maxima, Crocea or Derasa?

Tridacna maxima: Consider it when you have a bright, secure location on a solid surface. Allow for growth and a permanently unobstructed path to the light.
Tridacna crocea: Remains comparatively small, but that does not make it an undemanding nano-aquarium clam. It needs strong light and a suitable firm surface for attachment.
Tridacna derasa: Often considered a more robust introduction to clams. It still needs good lighting and can grow very large; a small purchase size should not hide its long-term space requirements.

Maxima and Crocea are particularly demanding of light. Derasa can often be kept under comparatively less intense lighting, but it does not belong in a dark corner. Species name or lamp wattage alone cannot determine the right location.

Check the location before buying

Start with three questions: where will the clam sit? Can its mantle receive unobstructed light there? Will that space remain clear as surrounding corals grow? A seemingly bright spot next to an expanding coral can look very different a few months later.

A PAR measurement at the intended location tells you more than the lamp's power setting alone. Also ask about the conditions in which the individual animal has been kept. Introduce new clams gradually to changes in lighting. Needing strong light does not mean placing a newly arrived animal immediately in the brightest spot.

Provide secure support and protect attachment

Maxima and Crocea need suitable firm support. Derasa is often placed on the sand bed. In either case, the clam should sit upright and securely, without its mantle rubbing against sharp edges. Provide water movement around the animal rather than a continuous hard jet against its mantle.

The attachment area underneath is delicate. Do not pull an attached clam off its rock. If it needs to be relocated, moving its support with it is usually preferable. Before buying, ask what the specimen is already attached to and how it can be positioned safely.

Plan for water chemistry and nutrition

Tridacna clams use light through their symbiotic algae and also take food from the water. Supplementary feeding cannot replace suitable lighting. Whether and how to supplement depends on the animal's size and the aquarium's food supply. Avoid adding large quantities of food as a precaution.

Shell growth consumes calcium and alkalinity. Track your readings, particularly as the clam grows or more calcifying animals are added. Our guide to stable alkalinity explains why consistent measurements are more useful than rushed corrections.

Choose the individual specimen

Compare the stated size, photographs and attachment information. A top-down photograph can look very different from a side view. For a WYSIWYG purchase, the individual reference number matters more than a general colour name. Our WYSIWYG buying guide helps you read photographs alongside product information.

Ask questions if the mantle or underside cannot be assessed clearly. Persistent unusual gaping, tissue injuries or small visible snails on the animal warrant closer inspection; they are not a diagnosis based on one photograph. Do not poke the animal or touch its mantle to force a response.

Unsure whether a visible slit is normal? Our guide to Tridacna openings and possible injuries explains what to look for and which photographs help assess a concern.

Common questions

Is a Derasa automatically beginner-friendly?

It can be a comparatively robust option, but still requires a suitable location, light and stable conditions. Allow for its eventual size in particular.