Recently, we got some new giant clams here at Bulk Reef Supply and are going to show you everything you need to know to acclimate and care for a giant clam in your reef tank.

When choosing a clam, it is best to get select a larger clam. Smaller clams are typically more difficult to keep and require more feeding. Larger clams, 3” or larger, are hardier and easier to acclimate into your home aquarium.  

Pay attention to the mantle; it should be evenly colored with no bleached areas or tears and a smooth edge. The larger inhalant opening in the mantle should by a slit, not wide open or gaping. If you are selecting the clam from your local fish store, wave your hand above the aquarium to block the light. A healthy clam should quickly react. For Maxima and Crocea clams, inspect the byssal organ, or foot, on the bottom of the clam to make sure it is intact and not damaged.

We recommend drip acclimating your newly purchased clam for about 45-60 minutes. The Innovative Marine AccuDrip works great and is super simple to use.

During this time you will want to inspect the clam closely for parasites and hitchhikers. The biggest concern for clam owners is the dreaded Pyramid Snail. These tiny snails,  no bigger than ¼ inch,  look like a grain of rice. They will attack and consume the mantle or flesh of the clam.  They reproduce very quickly and can be really difficult to remove. Be sure to check under the clam by the foot and all around the shell for the snails and their egg sacs.  

The shell of the clam can also hold a variety of other parasites and hitchhikers such as Aiptasia anemones, bristle worms, and nudibranchs. If you do find any hitchhikers you will want to physically remove them before placing the clam into your tank. A tooth brush and a pair of tweezers works really well. Be sure to clean the clam thoroughly in a separate container.

When placing a clam in your tank it is important to know the exact species of clam you have. Crocea and Maxima clams are found in rocky habitats, so they should be placed in the rock work or on hard substrate. They have byssal glands (foot) that will need to attach to a solid surface. Derasa, Squamosa and Gigas clams are best placed on sandy substrate and typically need less intense lighting.

Since we have Tridacna maxima clams, I placed them in the rock work. We want to place them in areas of lower lighting to allow them to acclimate because they are new. If placed under too much light, they can ‘bleach’ and lose their zooxanthellae.

We also have a small Derasa clam that has been thriving on the sandbed.

No matter the species, the clam should be placed on a horizontal surface that exposes the entire mantle to light because clams rely heavily on photosynthesis. Certain clams do have a foot and can actually move around your tank. It will take a few days for the clams to attach. Using some rubble rock (or the clam mount we offer on our website) to prop the clam up helps prevent the clam from falling over until it attaches. Keep clams away from other aggressive corals. Also be sure your tank does not house any clam predators. Certain wrasses and angelfish have been known to attack and devour clams in an aquarium. Remember to give your clam plenty of room to grow. Mature Tridacnids can grow quite large.  

A healthy clam will open with the mantle fully exposed during daylight hours. Because clams rely heavily on photosynthesis, they do best in aquariums with high output lighting. Maxima and Crocea clams require more light, while Derasa, Squamosa and Gigas clams require a little less light. But, all tridacna clams have relatively high light requirements. Research your newly purchased clam and place the clam according to its lighting requirements.

For water flow, you do not want a strong direct current blasting the clam as this will surely stress them out.  I find that if the mantle is moving around and flapping in the current, your water flow is too strong. If so,  then you will want to move it to a calmer area of your aquarium.

Although giant clams are mostly photosynthetic, they also filter feed; they will filter out particulate organic matter from your water and absorb organic compounds from the water such as nitrate, phosphate, and ammonia.

Feeding small particle foods such as phytoplankton will help to boost health and promote the growth of your giant clams.

The PhycoPure Zooxanthellae from Algagen is the first and only product of its kind. It contains a blend live zooxanthellae algae. It has been reported to have excellent results in helping clams and corals to recover from stress as it replenishes lost/expelled zoanthellae. It also helps to increase the coloration of clams and corals.

The Algagen PhycoPure Phytoplankton, Algagen Coral Smoothie, Brightwell Phytoplankton and other phytoplankton products are also great for giant clams.

Once the clam has acclimated to your aquarium, it can begin to grow quickly. Make sure to provide it with proper levels of calcium and alkalinity for growth as they will consume this quickly. Regular additions of iodine will also help with growth and coloration.

If you have a new clam or are thinking about adding one to your tank, Bulk Reef Supply is here to help! Please feel free to contact our friendly support team at 1-800-566-3474 or send an email to Until next time, take care and happy reefkeeping.