At a glance the quick version
Shell length. Wikipedia says large specimens rarely exceed 20 cm; SeaLifeBase gives a common size of 25 cm and a maximum of 41.7 cm.
Looks how to spot one
Heavy ridged shell with a fleshy, coloured mantle
A clam with a thick, scalloped shell that often sits partly buried in rock. When open it spreads a velvety mantle over the edge of the shell, patterned in vivid blue, green, gold or brown.12
Personality what they are like
Completely peaceful. It may shift position at first, then settles and should be left where it chooses to attach.3
Daily activity how busy a day looks
Sessile once settled; it opens and closes its shell and mantle with the light.3
Grooming and care the hands-on bits
Give it very strong lighting and stable reef water. Clams over about 5 cm usually need no extra feeding. Avoid tankmates that pick at clam mantles.3
Home where they are happiest
A mature reef tank with intense light and low to medium flow, placed on rock or sand high enough to get plenty of light. In the wild it lives on sunny reef flats and lagoons at about 0-35 m and 23-30 C.23
Food basics what goes in the bowl
Most of its food comes from zooxanthellae, algae living in its mantle that turn light into sugars. It also filters phytoplankton and takes up dissolved nutrients.123
Company who they like around
Lives alone and does not need company; it is peaceful toward all tankmates.3
The story where it all began
Peter Friedrich Röding described the species in 1798. It is the most widespread giant clam, and its bright mantle and modest size made it a favourite reef-aquarium clam; many in the trade are now farm raised.13
Fun facts for the dinner table
- 1
It starts life as a male and becomes a hermaphrodite at about 15 cm long.1
- 2
Spawning is cued by the moon, the time of day and eggs or sperm from nearby clams.1
- 3
Shiny reflective cells in the mantle may shield it from strong sun or help its algae.1
- 4
It is called the small giant clam because it looks like the huge giant clam but stays far smaller.1
Recognised by the official bits
- Taxonomy (via Wikipedia)
- First described by Röding in 1798 (as Tridachnes maxima); a giant clam in the family Cardiidae.1
- CITES
- Listed on Appendix II, so international trade needs permits.1
- IUCN Red List (via SeaLifeBase)
- Least Concern.2
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Maxima Clam. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingDepends on species, many feed from the light and the watervaries
- Salinity checkevery week
- Water testevery week
- Top-upTop up evaporation with fresh RO water, not salt waterevery day
- Water changeAbout 10 to 20% of the waterevery 2 weeks
- Light checkevery month
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- Tridacna maxima (Wikipedia) en.wikipedia.orgused for names, range, size, mantle, nutrition, reproduction, CITES, history
- Tridacna maxima (SeaLifeBase) sealifebase.seused for maximum size, depth, temperature, range, IUCN status
- Maxima Clam (Saltwaterfish.com) saltwaterfish.comused for aquarium care, lighting, flow, placement, feeding
- Clams category (Saltwaterfish.com) saltwaterfish.comused for mantle colour forms offered
Checked 2026-09-30. Text is written in our own words from these sources.