Maxima Clam, Tridacna Maxima, Elongate Giant Clam
Tridacna maxima

The Maxima Clam is the third largest clam, andit’s popularity is due to it’s “no two are alike” patterned mantles!

The Maxima Clam Tridacna maxima is one of the most beautiful of the Tridacna clams. It’s also one of the most readily recognized of the giant clams in the aquarium industry, and has been dubbed by some enthusiasts as the “Holy Grail of Reef Aquariums.” Maxima Clams usually show a variety of rich colors and patterns that are highly variable and exotic. It is a favorite for many aquarist and much of Its popularity is due to the “no two are alike” patterned mantles.

Colors include combinations of blue, brown, green, gray, purple and yellow. Patterns can be stripes, blotches, or spots. There are usually larger areas of solid color in the Maxima, more so than in other Tridacna clams. Solid blue Maxima Clams have been found in the Red Sea. One marking often seen on the Maxima Clam is a prominent row of black pigmented eye spots along the edge of the mantle. But though these markings are common, they shouldn’t always be expected.

This gorgeous clam is also known by the common names Elongate Giant Clam, Great Clam, Rugose Clam and Small Giant Clam. Yet with some specimens being so intensely colored and strongly patterned, you will find references to them in the aquarium industry under a variety of descriptive names such names as Ultra Maxima Clam, Wild Ultra Blue Maxima, Blue Maxima, Golden Maxima, Teardrop Maxima, and Zebra Maxima.

The gorgeous colorings of its mantle arguably make it one of the most popular of the Tridacna clams. Vying for this honor is its close cousin, the Crocea ClamTridacna Crocea. Though a bit smaller than the Maxima Clam, the Crocea is another highly colored, beautiful, and favored giant clam.

The Maxima Clam will generally reach a maximum of about 12″ (30 cm) in length in captivity, though specimens can reached between 14 to 16 inches (35 – 40 cm) in the wild. It is the third largest giant clam following its cousins, the massive Gigas ClamT. gigas which reaches over 3 feet in length, and the huge Derasa ClamT. derasa. However it grows at a much slower rate. On average this clam will only grow .08 to 1.6″ per year, rather than the 4″ per year seen with those two big fellows. To even reach a 14″ (35 cm) length can take it 50 to 60 years.

The Maxima Clam is also not as hardy, nor as easy to care for, as its two large cousins but is slightly more durable than the smaller Crocea Clam. In most regards, its care and maintenance are also similar to that of the Crocea, making it best suited for the intermediate to advanced aquarist. This clam needs strong lighting with a Kelvin range between 6K to 10K, a turbulent water flow, and very stable water conditions.

For more about keeping Tridacna Clams, see:
Giant Clam Care: Caring For Tridacnid Clams

Maxima Clam, Tridacna maxima, Tahiti super color clams

Report Broken Video
Many colors in a dealers tank

This video shows that Maxima Clams are like fingerprints, in that no two ever look the same! They have light sensors on the mantle and do need a lot of lighting. Keep your tank kelvin range from 6K to 10K for best results. They do best in a tank that is at least 100 gallons. Maxima Clams can live over 200 years and will reach 14″ around 70 or 80 years, however most do not live that long in captivity and will more than likely grow to around 8 to 9″ in most aquarists tanks during their first 30 years.

Maxima Clams – Quick Aquarium Care
  • Minimum Tank Size: 100 gal (379 L)
  • Aquarist Experience Level: Intermediate
  • Temperament: Peaceful
  • Temperature: 74.0 to 83.0° F (23.3 to 28.3&deg C)
  • Size of organism – inches: 15.8 inches (40.01 cm)
  • Diet Type: Omnivore
  • Suitable for Nano Tank: No

Habitat: Distribution / Background

The Maxima Clam Tridacna maxima was described by Röding in 1798. They are found throughout the Indo-Pacific, as far north as southern Japan, as far south as the Great Barrier Reef. In the west they are found from East Africa and the Red Sea to Pitcairn Island in the eastern Pacific, and then as far east as Polynesia. Pitcairn Island is a volcanic island in the South Pacific near the Tropic of Capricorn. Polynesia is in the central and South Pacific oceans and contains the Hawaiian islands, Tonga, Samoa, and the islands of French Polynesia.

The T. maxima are the most common and widespread of the giant clams. They are listed on the IUCN Red List as Least Concern (LC), with the designation Lower Risk/conservation dependent (LR/cd). Other common names they are known by are the Great Clam, Elongate Giant Clam, Giant Clam, Rugose Clam, and Small Giant Clam.

They are the most widely distributed and the most colorful giant clams, but are also being aquacultured for the marine trade. With some specimens being intensely colored and strongly patterned, you will find references to them in the aquarium industry under a variety of descriptive names. They will be called such names as Ultra Maxima Clam, Wild Ultra Blue Maxima, Blue Maxima, Golden Maxima, Teardrop Maxima, and Zebra Maxima.

In the wild, the T. maxima‘s are found on the tops or slopes of the reef in shallow and clear waters. While they can be found at depths of 50 feet (15.24 m), their numbers drop off dramatically at 25 feet (7.62 m). They are often living together in the much shallower great congregations. However in the deeper waters, over 25 feet, they are found solitary (Jaubert 1977).

They occur on limestone substrates, coral rubble, or on top of living corals. When they are very tiny, just settling into a reef, they will chemically borrow and make a small divot that their shells fit in perfectly. They will have bored themselves slightly into the coral rock or substrate on which they sit and will be firmly attached by their byssus glands. They lose their desire to burrow, however, when raised in captivity, and only use their byssus (foot) to attach to hard surfaces.

Giant clams are filter feeders. They will filter water to extract phytoplankton and microscopic organisms that inhabit the sunny upper waters, such as dissolved organic matter like ammonium nitrate. However, their largest source of food comes from the sun and the zooxanthellae found in their mantle. Predators are small pyramidellid snails that bore into their tissue and feed on their bodily fluids. While this is less of a problem in the wild, it is more of an issue in enclosed systems.

  • Scientific Name: Tridacna maxima
  • IUCN Red List: LC – Least Concern


Maxima Clams are the third largest of the giant clams. They usually grow to an average length of about 12″ (30 cm), though they can reach between 14 to almost 16 inches (35 – 40 cm) in the wild. But they are slow growers, expanding at only a few millimeters per month.

Giant clams are all born male and then turn female as needed. The Maxima clams become sexually mature around 3,” which is around 2 to 5 years of age. But because these clam only grow at a rate of .08 to 1.6″ per year, to even reach a 14″ (35 cm) length can take 50 to 60 years. Many aquarists have kept Maxima Clams for decades, however this genus may live over 200 years in the ocean.

Blue Tridacna maxima
Blue Tridacna maxima

Maxima Clams have a soft, laterally compressed body that is enclosed in an elongated shell. The shell consists of two parts connected by a short hinge. The hinge has an opening, called the “byssal opening,” where a muscular foot attaches to a hard surface. This muscular foot slowly burrows into the reef at the place where the clam settled during its larval stage. These clams do not burrow in captivity. Because they do not burrow when tiny, they wont do it at all, and will use their byssus (foot) to attach to hard surfaces.

The shell of the Tridacna maxima can vary depending on the environment they are in and the crowding of corals and other clams nearby.

Some characteristics of Tridacna maxima’s shell:

  • usually asymmetrical and elongated
  • three times longer than they are broad
  • they have a short hinge
  • they have a large byssus gland opening
  • scutes are usually low and close together
  • the lateral distance between scutes in adjacent rows is usually less than the scutes’ width
T. crocea
Photo © Animal-World

Giant clams have no head, but their soft body consists of a mantle forming an outer wall that encloses a visceral mass containing the body’s organs. The mantle protrudes in the form of flaps that are quite colorful. A siphon, also called the intake siphon or inhalant siphon, is a fleshy tube-like structure that is part of the mantle. The intake siphon is used to direct water flow into the mantle cavity and across the gills. The inhalant siphon on the Maxima has small, fine tentacles.

The mantle of a Maxima Clam can be any colors of the rainbow, including black and white. It will sometimes exhibit an undulating shape with tubercles that are light sensitive. Although it is rare, the tubercles are sometimes quite numerous. This is a distinct feature that only the Maxima Clams have. They look like little “eyes” around the edge of the mantle, and are often incorrectly called “eyes.” But these are actually hyaline organs, e translucent windows that allow more light onto pockets of zooxanthellae, thus increasing the clam’s metabolism.

Purple Tridacna maxima
Purple Tridacna maxima:

Maxima Clams are often confused with the Crocea ClamT. crocia. When they are both small, the Maxima and Crocea can only be differentiated by dissection. This is because on small specimens, the color patterns of these two clams is similar and the outside of the shell is identical. Their differences can be determined by their shells and their byssus glands once they get older. As they mature, the shells of the Maxima and Crocea Clams become much different.

Comparing Maxima Clams to Crocea Clams:

  • If the clam is over 6″ it is a Maxima, as Crocea Clams never get that large.
  • A Maxima Clam will never have the entire mantle background in a striped pattern.
  • Maxima Clams usually have a more elongated shell.
  • The scutes of T. maxima are more pronounced and they cover most of the shell.
  • The byssus gland of the Crocea Clam is very long and wide, the Maxima will have a smaller byssus opening.
  • The byssus opening on the Maxima extends towards the edge of the shell, but not as much as on the Crocea.
  • The byssus opening’s edge on the Maxima tends to curl upwards with a chitonous ring surrounding it.

Maxima Clams can also be somewhat confused with the Squamosa ClamTridacna squamosa. Young Squamosa and Maxima Clams are mostly confused because both have scutes on their shells.

Comparing Maxima Clams to Squamosa Clams:

Compared to the Squamosa ClamTridacna squamosa, the shell of the Maxima Clam is asymmetrical. Young Squamosa Clams are sometimes confused with the Maxima mostly because both clams have scutes on their shells. The rows of scutes of a Maxima Clam are smaller and closer together than those on the Squamosa, and the hinge on the Maxima is smaller.

  • The shell of the Maxima Clam is asymmetrical, while the Squamosa Clam is symmetrical.
  • The rows of scutes of a Maxima Clam are smaller and closer together than those on the Squamosa.
  • The hinge on the Maxima is smaller than on the Squamosa Clam.
  • Size of organism – inches: 15.8 inches (40.01 cm) – The average size is about 12″ (30 cm), but can reach 14 to 16 inches (35 – 40 cm) in the wild. They are sexual mature between 2 to 5 years (around 3″ in size), but are very slow growers, taking 50 or 60 reach 14.”
  • Lifespan: 200 years – May live decades in captivity, but can live over 200 years in the wild.

Difficulty of Care

The Maxima Clam is beautiful, but moderately difficult to care for, so it is not suggested for a beginning aquarist. It is a bit easier to care for than its close relative, the Crocea Clam, but both species need diligent attention paid to water parameters, flow, salinity and lighting to be stable, more so than some of the other Tridacna clams. They do not like strong laminar water movement and should be placed in a part of the tank where there low linear flow or a moderate turbulent flow. Still, most have a poor record for long term survival, so they are recommended for the intermediate to advanced aquarists.

Its best to obtain a captive grown clam that is at least 2 inches, ideally 4 inches, in length. Smaller specimens do not ship well nor do they adapt as easily. If obtaining a clam from the wild, you will have a much better chance of success if you receive it still attached to a rock. When a healthy Maxima Clam is obtained, with carefully handling and proper lighting it will establish itself. When first obtained, inspect the clam’s shell for predators. It is important to make sure they are not being irritated or fed upon by other organisms. Clams can be sensitive handling, so avoid that as much as possible.

They are best positioned on a hard surface as they are not sand dwellers. If your newly acquired clam is predominately brown and showing little of its normal coloration and patterning, it should be placed lower in your tank away from strong lighting. The brown coloration is the clam’s zooxanthellae showing and is probably due to the clam losing its protective coloration during shipping. While they will adjust to their new surroundings in time and will become more hardy, during acclimation it is especially important to avoid wide fluctuations in light, water flow, reef water parameters (calcium, magnesium etc), and salinity.

If they are positioned where the water flow causes them to fold their mantle upward or close, this will cause the clam to eventually starve and die. Their coloring is incredible but they are also one of the most demanding clams when it comes to lighting. Once they adjust to the lighting, which is suggested at 400W metal halide or a high intensity LED, the light must stay constant. The mantle will extend excessively if the light is not strong enough. If you need to move them, take a few weeks to slowly get them into their new position or they will go into shock.

  • Aquarium Hardiness: Moderately Difficult
  • Aquarist Experience Level: Intermediate

Foods and Feeding

Most clams fulfill their nutritional requirements by filter feeding and absorbing dissolved organic compounds from the water. The Tridacna clams have gone even further than this, using zooxanthellae to manufacture food for themselves. They receive the majority of their nutrition from their zooxanthellae. Yet research has shown that all Giant Clams that are under 4″ do not have enough mantle tissue to provide enough space for zooxanthellae to keep the clam alive.

Some feel that mature Maxima Clams do not require feeding in the aquarium. Whether additional feeding is required is still debated. Some hobbyists believe they should be fed, going on the assumption that they are filter feeders like other clams. Basic nutrients in the aquarium that giant clams need are calcium, strontium, iodine, and a minute amount of nitrate that is at least 2 ppm. They will not thrive at a level of 0 nitrates.

Four ways clams make food for themselves:

  • These clams have large amounts of zooxanthellae that live in their tissues. With plenty of light this algae will make too much food for themselves and the extra carbon and glucose is given to the clam (similar to most reef corals).
  • The actual zooxanthellae themselves can be eaten by amoeboid cells within the host clam if needed.
  • Giant clams have the ability to absorb nutrients like ammonia, nitrate and phosphates from the water.
  • Giant clams are filter-feeders, straining fine particulates like phytoplankton, zooplankton and detritus from surrounding waters with their specialized gills.

Clams under 2″ to 4″ need regular feedings of phytoplankton. It is suggested that they be fed micro-foods designed for filter feeders, especially when small. A yeast-based suspension that has been mechanically whisked, live phytoplankton or commercially prepared micro-foods like ‘marine snow’ or ‘reef snow’ can be offered.

Once they are older they will still benefit from phytoplankton foods fed on a regular schedule in an aggressively skimmed tank. With plenty of fish present, direct feeding is not as critical once they are over 4″ long. When there is a good fish population, most clams fulfill their nutritional requirements by filter feeding and absorbing dissolved organic compounds from the water. For more information about the feeding process of Maxima Clams see What Do Clams Eat.

  • Diet Type: Omnivore – Nutrition is obtained through filter-feeding of phytoplankton, zooplankton and detritus along with lighting and the marine algae, zooxanthellae.
  • Flake Food: No – Will not eat this food.
  • Tablet / Pellet: No – Will not eat this food.
  • Live foods (fishes, shrimps, worms): Some of Diet – Clams under 4″ will need live phytoplankton to thrive.
  • Liquid Foods: Some of Diet – Marine snow or other phytoplankton substitutes, especially if there are no fish. Lighting and the marine algae, zooxanthellae, make up the rest of the food.
  • Meaty Food: Some of Diet – Zooplankton and Phytoplankton in the water. The rest comes from lighting and the marine algae, zooxanthellae.
  • Feeding Frequency: Daily – Daily for clams up to 2″ and several times per week for clams up to 4″ is recommended. Can be fed weekly when full grown, but do not feed if there are plenty of fish in the tank.

Aquarium Care

Good water quality must be maintained, but if a healthy Maxima Clam is obtained and proper light provided, they are moderately easy to keep. Stable tank conditions are required to keep the clam healthy. With careful attention paid to water parameters and proper lighting, Maxima Clams require require little else in the way of care. Do typical water changes of 10% biweekly, 20% a month, or 5% weekly. It has been noted that 5% weekly water changes replenish many of the needed additives.

Basic nutrients in the aquarium that giant clams need are calcium, strontium, iodine, and a minute amount of nitrate. Along with regular water changes the following parameters are important in keeping your Maxima Clam long term. Adding large doses weekly is not recommended. Daily doses or adding to top off water is best:

  • Calcium: Calcium is the main building block for clams and should be present in the water at levels of at least 280 mg/L for growth to occur. Seachem’s calcium additive works at 385. More rapid, natural growth is seen when calcium is in the range of 400-480 mg/L.
  • Strontium: Strontium is incorporated in the shell along with calcium and should also be provided for optimum growth.
  • Iodine: The addition of iodine to the aquarium will also enhance growth and color. Use caution, as iodine spikes have been known to kill them. Add iodine with top off water or dose daily, but not at one time in a big weekly dose.
  • Nitrate: They require some nitrogen for proper growth. They will not thrive at a level of 0 nitrates. Nitrate can be added if levels are extremely low, but be careful as nitrates should never exceed 2 mg/L. Provide a minute amount of nitrate that is at least 2 ppm.

Maxima Clams can handle strong water motion and relatively strong fluctuations in water parameters, but you really don’t want your water parameters to fluctuate too much.It is also important to make sure they are not being irritated, and not being fed upon by other organisms. Keep a watch for predators as this clam can be easy prey with its large and wide byssal gland opening.

Maxima Clams are sensitive to being handled so avoid it if at all possible. it will attach itself to the substrate in less than a day. Keep this in mind when placing your clam in the tank. Make sure you put it where you want it to stay. Damage could be done when messing around with an attached clam. For more in depth information on caring for Maxima Clams see, Caring For Tridacnid Clams.

  • Water Changes: Bi-weekly – To keep water stable, test weekly.
  • Calcium Levels: 400.0 – 450.0 ppm – If using Seachem’s calcium, 385 should suffice.
  • Alkalinity Levels: 8.0 – 12.0 dKH – Best at 9
  • Magnesium Levels: 1,250.0 – 1,350.0 ppm – Adjust magnesium levels before checking calcium levels.
  • Strontium Levels: 5.0 – 15.0 ppm
  • Iodine Levels: – .030 to .060 ppm: Control is not recommended.

Aquarium Setup

Maxima Clams can be kept in a reef environment with live rock. Placing a Maxima Clam in your tank is pretty much the same as placing a Crocea Clam. They should be placed on live rock or some other solid material they can attach to. In the wild, these clams burrow into rock and rely heavily on their byssal threads for attachment. They will eventually bore into a substrate or other substance on which they are placed. However, they lose the need to bore into rock if they are captive grown. They can handle strong water motion and relatively strong fluctuations in water parameters, but high pH and high temperatures can cause problems.

The size of the tank should be at least 100 gallons for your Maxima Clam (though larger is better) as this will help keep water parameters stable. Live rock is necessary and sand is preferred if they will be on the substrate. A mature tank is also important. The tank should be at least 6 months old from the time of adding that last piece of live rock. Once you see Coralline algae growing (that cool pink and purple hard algae) you know your tank is doing well and ready for your clam.

These clams need diligence attention paid to their water parameters, water flow, and salinity, and the lighting needs to be stable. Water movement should not be a constant linear flow. Placing the clam in mild turbulent, or even “dead zones,” that are exposed to strong light is best. Clams that close partially or all the way are not happy with water flow. If they are positioned where the water flow causes them to fold their mantle upward or close, this will cause the clam to eventually starve and die.

When placing your clam into the tank, do not put it in a tight crevice. This may prevent it from opening fully, or if it moves too much, it can fall behind the rock work. If putting them in a hole in the rock work, keep excess detritus out by periodically using a turkey baster or power head. If you have plenty of light on the substrate, placing them on a flat rock below the sand is best. Put a flat rock on the bottom glass of the tank and the clam on top of that. That helps to stabilize them and if you have to move them, the small rock makes it easier. Fill in the area with sand, as much as half way up the clam, to keep their byssal opening blocked off. This helps prevent pests from attacking them through the opening.

Lighting is one of the most important aspects in maintaining Maxima Clams. Pay attention to the color of the clam’s mantle and use that as your judge for where your clam should go. While one Maxima Clam may do well in a tank with one type of lighting, another may not. Some will show vivid coloration. another may be showing off the brown color of their zooxanthellae. If your clam’s color is iridescent, it has adapted to bright lighting and should be placed closer to the top of your tank. If your clam is mainly brown, it should be placed lower in your tank away from strong lighting. The brown coloration is the clam’s zooxanthellae showing and is probably due to the clam losing its protective coloration during transport. If you need to move them, it should take a few weeks to slowly get them into their new position or you will shock them. You will see their mantle extending excessively if the light is not strong enough.

Coming from shallow waters in the wild, these clams will need intense lighting. Kelvin is best at 6K to 10K, to mimic the light levels they receive naturally in their shallow habitat. Provide very strong lighting, such as 400W metal halides or intense LED lighting if they will be towards the bottom of the tank. If you plan to keep these clams under fluorescent lighting, keep them close to the top of the tank, and the lights. Be sure to protect the lights from their inevitable squirt of water if they become startled. Once they adjust to the lighting, the light must stay constant.

A stable salinity is critical, aim for 1.024 to prevent swinging out of the 1.023 and 1.025 range. Automatic fresh water top offs are highly suggested to keep salinity stable. Keep pH at 8.1 to 8.3, do not let the aquarium exceed a pH above 8.4. For hardness, maintain a dkh of 7.9-12, with the optimal being 9. A temperature between 74 to 83ËšF (23 to 28ËšC) is best, but be sure to keep the temperature you choose stable.

  • Minimum Tank Size: 100 gal (379 L) – Tank should be at least 6 months old, preferably with coralline algae growth.
  • Suitable for Nano Tank: No – Water will not be stable enough.
  • Live Rock Requirement: Typical Amount
  • Substrate Type: Sand
  • Lighting Needs: High – Strong lighting – Kelvins: 6K to 10K to mimic the light levels they receive in the shallow habitats of their natural environment.
  • Temperature: 74.0 to 83.0° F (23.3 to 28.3&deg C) – Keep the temperature stable.
  • Specific gravity: 1.023-1.025 SG – Salinity is important, too high or low a salinity can cause the death of a clam. Stay within this range, aiming for 1.024.
  • Water Movement: Moderate – Maxima Clams can handle strong water motion, however high currents should not be a constant condition. Weak linear is okay, though moderate and turbulent is best.
  • Water Region: All – Dependent on lighting.

Social Behaviors

Clams are very stationary and peaceful, they are not aggressive towards other aquarium inhabitants. Though they have the ability to shut completely, they do need protection from anemones and some corals. They should not be kept near any stinging cell creatures and must be kept away from any sweeper tentacles. Anemones need to be watched, as they can move close to a clam and sting or eat it.

Maxima Clams commonly have small shrimp and crabs that live in the mantle cavity. They are considered ectoparasites or commensals, and they will not harm a healthy clam. Be cautious with tank inhabitants that may pick at the clam or eat its mantle, such as Trigger Fish and Puffers. Blennies, Butterfly Fish, Clown Gobies, Angelfish and shrimp may disturb Tridacna clams.

  • Venomous: No
  • Temperament: Peaceful
  • Compatible with:
    • Same species – conspecifics: Yes
    • Anemones: Monitor – Protect the clam from anemones that wander.
    • Mushroom Anemones – Corallimorphs: Monitor – Safe as long as they do not come in contact with the clam.
    • Leather Corals: Monitor – Should be okay if spaced apart.
    • Zoanthids – Button Polyps, Sea Mats: Monitor – Should be okay if spaced apart.
    • Sponges, Tunicates: Safe
    • Shrimps, Crabs, Snails: Monitor – Small commensal shrimp are fine if the clam is healthy. Remove any small, rice-sized snails found on the clam’s surface with a toothbrush.
    • Starfish: Monitor – Starfish usually only eat dying organisms.
    • Feather Dusters, Bristle Worms, Flatworms: Safe
    • Clams, Scallops, Oysters: Safe
    • Crabs: Monitor – Tiny commensal crabs are okay on a healthy clam, avoid other crabs.
    • Snails: Monitor – Make sure nassarius snails cannot turn a substrate living clam over. Remove parasitic pyramidellid snails, other snails are safe.
    • Sea Apples, Cucumbers: Threat – The clam will die if these species expel their toxins. Giant clams are much more sensitive to these toxins than other invertebrates, even if the system is large.
    • Urchins, Sand Dollars: Monitor – Should be safe, but it is unknown if any or all species are safe.
    • Nudibranch, Sea Slugs: Monitor – Should be safe, but it is unknown if any or all species are safe.
    • Copepods, Amphipods, Mini Brittle Stars: Safe
    • Stony Corals: May be aggressive – Only safe as long as they do not come in contact. Stony corals can sting your clam.
    • Soft Corals: May be aggressive – Give clam plenty of space.

Sex: Sexual differences

There are no discernible sexual differences.

Breeding / Reproduction

The giant clams are protandry, meaning they are born male and change to female. Clams will release eggs and sperm that can number into the tens of thousands of eggs. This event tends to happen around sunset. One aquarist noted a spawning clam pulsing out eggs every two minutes. Once the eggs are externally fertilized, the embryos develop into trocophore larva, which are free-swimming. The next stage is the bivalve veliger, which sort of looks like a tiny free swimming clam.

They will find a shallow area of the reef to settle into, using limestone substrates on coral rubble or on top of living corals as their new home. They will slightly burrow into these hard surfaces. If they do not burrow early in life, they loose the tendency.

Maxima Clams have been propagated in captivity, and the demand from aquarists has raised interest in producing colorful varieties of all the species. Typically, there is some sort of outside stimuli that causes spawning, which can be a change in temperature, salinity, or other parameter. However this should be left to the experts, as clams spawning in a small system can cause serious pollution issues. For detailed information of tridacnid propagation, see Giant Clam Breeding and Reproduction

  • Ease of Breeding: Difficult

Ailments / Diseases

Keep a watch out for predators! The Giant Clams can be easy prey with their large and wide byssal gland opening. The most dangerous predators are the highly prolific pyramidellid snails of the Tathrella, Pyrgiscus, and Turbonilla genera. These are parasitic snails about the size of a grain of rice or smaller, rarely reaching a maximum size of about 7mm in length. These snails attack tridacnids with a trunk-like snout called a “proboscis.” They punch holes into the clam’s soft tissue and then feed on its bodily fluids.

While in nature, giant clams can deal with a few of these parasitic snails, in captivity these snails tend to multiply to dangerous numbers. They may hide in the scutes of the clam or in the substrate by day, but will often will be found around the edges of the clam’s mantle tissue or byssal gape (large foot hole) after the lights go out. They can produce numerous small, gelatinous, egg masses on the clam’s shell. These masses are transparent, so difficult to spot. Before putting it in the tank, scrub your clam’s shell vigorously with a toothbrush, or other brush with firm bristles, to remove the snails and their eggs. Be careful not to scrub the clam’s soft tissues, as that can cause injury and lead to infection. Inspect your clam regularly for several months and remove any snails you discover.

Some other common ailments of Maxima Clams:

  • Pinched Mantle: Another common affliction of giant clams is called the Pinched Mantle disease. The edges of the mantle become pinched and contorted, and the margins won’t extend fully. This condition almost always results in death unless treated, and it can spread to other clams. The actual cause of this ailment is unknown, but it may possibly be an attack by some sort of protozoan. An easy treatment, that is is stressful but effective, is to submerse the clam in a freshwater dip for a few minutes. Signs of recovery can take a day or two.
  • Bubble Mantle: Caused by laminar flow directed at the clam or pouring water directly into the aquarium in a way that causes bubbles to form (use a siphon and water pump and/or pour very slowly and carefully or pour into sump only). These bubbles can get stuck in the clam’s mantle with can cause illness and death.
  • Gaping: The larger of the two holes is gaping open, larger than normal. This is usually due to poor water quality. Stability of your water parameters need to be checked quickly and addressed.

Giant clams are also quite sensitive to chemicals or toxic substances dissolved in the water, so be sure to maintain good water quality. As mentioned under aquarium care and aquarium parameters above, high pH, high salinity, and high temperatures can also cause problems. Avoid large weekly doses of anything, especially iodine, which has been known to kill them. For in-depth information on potential Tridacna clam problems, see: Tridacnid Clams: Friends, Enemies & Ailments


Maxima Clams obtained from aquaculture systems are readily available, and usually from 1 1/4″ to 3 1/4″ in size. They can be found online and in stores, Due to the wide variety of colors and sizes, they range in price from moderately expensive to expensive.

Maxima Clams from the wild are seasonal. Because they burrow into the rock and attach themselves with their byssal threads, collecting them from the wild is more difficult and the chances of receiving a damaged clam are greater. Once the byssus gland is damaged, the clam doesn’t usually live long. This is most likely due to bacterial infections, however, rather than the damage itself. You will have a much better chance of keeping a wild collected clam if you receive it still attached to a rock.


 Almeja gigante (Tridacna maxima) (Image Credit: Diego Delso, Wikimedia Commons CC BY-SA 4.0 International)