Close up of a Derasa Clam Spout

Derasa Clam Care

The Derasa Clam (Tridacna derasa) is the second-largest clam of the Tridacna clams. It is also one of the easier clams to care for. This clam can grow to about 20 inches in captivity. They typically have a brown gold coloration with white stripes or spots. It may also have bright blue along the outline of the mantel. It is possible to find specimens with blue and green highlights as well. The beauty of this clam and its “easier than most” label might make you want to rush and buy one now, but there are some important things you should now about Derasa Clam care before you do so.


The wild population of Derasa Clams is listed as vulnerable because they were hunted for food. Luckily, they are widely aquacultured within the reefing industry. While many clams that are aquacultured are for the reef aquarium hobby, most of them are for food. Either way, they are not commonly collected from the ocean because of them being aquacultured. This is great for the clam populations in the wild.

In the wild, Derasa Clams can grow to twenty-four inches! They are found in the Indo-Pacific, Central Pacific, and South Pacific. They usually live in the outer areas of the reef at depths between one and sixty feet. They will live on sandy substrate, on rocky surfaces, or among corals. Since these clams like lots of light, they will most commonly live in open areas where they are not covered or shaded in any way. These clams may live alone or in groups as dense as thirty clams per hectare.

Why Captive Bred Derasa Clams Are Best

The National Marine Fisheries Service (NMFS) and the National Oceanic and Atmospheric Administration (NOAA) have the Derasa Clam and other Tridacna clams labeled as threatened or endangered. For the Derasa Clam, this is mostly because of overutilization for commercial purposes such as food production or collection for aquariums. Buying captive-bred clams (or any saltwater creature) is best because it limits human-caused harm on the wild populations of clams.

If you, for some reason, couldn’t care less about the wild populations (you should care!), there are still many reasons to buy captive bred Derasa Clams. First, they are more accustomed to aquarium life and have a much higher chance of surviving and thriving in a reef aquarium. They are less likely to get diseases and do better withstanding shipping or transport stress. It looks like captive bred is the best and only way to go!

Derasa Clams are widely aquacultured and finding a captive bred specimen is not all that rare. You do want to ensure that you are buying your clam from a reliable source. Some clams may come with fish parasites and other pests on them. When you buy your clams from AlgaeBarn, the clam you receive is much less likely to have unwanted hitchhikers or pests. This is because AlgaeBarn keeps their clams in invertebrate-specific systems.

Water Quality

Water quality is key when it comes to keeping a Derasa Clam successfully. They require very clean water. There should not be particles or debris floating around in the tank. To achieve sediment-free water, make sure your filtration is capable of filtering such things out.

The nutrients in the water should also be low. Derasa Clam care usually requires nitrates under 2 ppm, but nowhere near zero, as they do need some nutrients. You may also want to consider how much you feed your tank when thinking about getting a Derasa Clam. If you have a fish or other organism that requires heavy feeding, you may want to reconsider. Heavy feedings can pollute the water and in turn irritate the clam.

Your water’s salinity, pH, and other aquarium parameters should be kept stable. Do this by testing frequently and using automation such as an auto top off. Using an auto top off is very necessary, not only for the care of your clam but for the whole tank and its inhabitants. There are many things you can keep stable with an auto top off. The most obvious is salinity. This is also the parameter that can fluctuate the most. It is silly to rely on your memory to refill the tank with freshwater using large amounts, while an auto top off will do it slowly as the water evaporates. You can also dose base elements, iodine, and other elements using an auto top off. It is best to do it this way because the nature of an auto top off is to add water slowly over time. That way you do not shock the clam and its tank mates. You will also want to try an keep the temperature stable. It does not matter exactly what temperature you keep it at, as long as it is between 72F and 78F. This may be difficult for people living in warmer areas, but having an air conditioner unit or a chiller can work. As for raising the temperature, it is as simple as using a heater.


Derasa Clams do best towards the bottom of the tank in the sand bed.You can also place them on the rock work, but make sure they are not at risk of being knocked over. It is also important to make sure that no detritus collects on the clam. One of the best ways to ensure secure Derasa clam placement is to purchase a Derasa Clam Keeper Kit.

They can usually handle more intense lighting, but for proper Derasa Clam care they should be acclimated to the lighting. There are several ways you can go about this. If you have LEDs and are able to control the intensity, you can start the intensity low when you first add the clam. Then, over the course of a few weeks gradually increase the intensity every day. Another way is to add layers of plastic screening between the light and the tank above where the clam is. Like with the other method, gradually remove the screens every few days.

The amount of lighting a Derasa Clam needs depends on its coloration. If it has a lot of bright blue, it will need much brighter lighting to maintain that color. The clams with a gold iridescent color can also handle more intense lighting. If the clam’s mantle is brown and is not showing the gold colorations, be sure to place it in lower light. When you find the correct intensity, keep it stable at that level. Whatever intensity you find yourself putting the clam at, don’t forget to acclimate it to that level first.

When it comes to water flow clams like moderate to strong water flow. This is important to keep any detritus from collecting on the clam. While it can handle strong water flow, it has to be random and not direct. It would better to have moderate water flow that is random and indirect than to have direct strong water flow.

The placement of a clam is something that takes careful planning and consideration. It can be the difference between a dead clam and a clam that doubles in size in a year.

Base Elements

Clams have a calcium-based shell and if you did not guess already, this means they need a lot of calcium to grow. They certainly will grow faster with higher levels, but it is more important to keep the levels stable. You can keep the level stable by dosing two-part, dosing kalkwasser, or using a calcium reactor. As mentioned earlier, if you have an auto top off, you can dose kalkwasser through that. This will be one of the best methods for smaller tanks as long as your auto top off does not fail. For larger tanks, it will be best to use a calcium reactor.

The calcium levels should be between 400 and 450 ppm, the alkalinity should be 8-12 dKH, and magnesium should be 1,250-1,350 ppm.


If it is under four inches, feeding is required for Derasa Clams. Smaller clams need to be fed phytoplankton a few times per week to keep them alive. When the clam gets larger it is still beneficial to feed the clam phytoplankton or just add it to the tank, especially if your nutrients are close to zero.

The beautiful Derasa Clam is one of the easiest Tridacna clams to care for, but it still needs careful planning before being added to the tank. Fortunately for you, you have more insight into Derasa Clam care after reading this article.

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