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Close up of a Derasa Clam Spout

Derasa Clam Care

by greg.chernoff

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.

Derasa, mouth open wide!Background

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.

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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.

Placement

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

Phytoplankton is a great derasa clam food!

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.

Feeding

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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Reader Interactions

Comments

  4. Alex von Hochtritt says

    That’s a gorgeous clam. I’ve never thought of having a clam in a tank before, that beauty – now I’m thinking about it.

    Reply

  19. Andrew Wiencek says

    Clams have always made me nervous, but after reading about them, I feel more comfortable and might end up getting one.

    Reply

  22. Kristen Maves says

    It’s nice to know when buying tank raised your still caring and getting a beautiful part of the ocean! Thank you for all the info this is next on my list ?

    Reply

  35. Chris Buswell says

    If one obtains a specimen without the gold or blue coloration, is it possible to encourage the clam to develop this as it matures?

    Reply

  49. Rudy A Garcia says

    Bookmarking this page for whenever I get a large enough tank in the future that can house one of these. Until then….I will just envy everyone that keeps posting pictures of their Derasas and Maximas.

    Reply

  59. T.Erickson36 says

    I never realized that their wild population is in danger due to harvesting for food. I would’ve thought it would’ve been more due to pollution. Also never realized that they need super clean water, especially with them being a filter feeder.

    Reply

  63. Garrett Keller says

    I ran out of Phytoplankton for 3 weeks while my clam was 3″ and thriving. Sadly, It all happened over night with no signs of stress, I lost my clam because of not having the phyto.

    Reply

  66. Matt Traylor says

    Always wanted to keep a nice clam, but was always scared I’d kill it. This is a nice article that gives me some hope that I will be able to do so! Thanks!

    Reply

  69. Josh Gay says

    Good to see more and more clams are being aquacultured. Thats what I feel we should all be working towards in the hobby, more and more propagation and aquaculture, less and less taking from the wild.

    Reply

  90. Mike B says

    Definitely a must have in my reefs. They stay in until they out grow the space. Quick growers but do take up the Calcium. Very hardy if you get them from a respectable source.

    Reply

  119. Drew Rollman says

    just saw a beautiful golden derasa at the lfs yesterday. I’ve never been a fan until I saw that one. always loved the ultra maximas

    Reply

  145. dcallahan56789 says

    Do you find that larger clams have a better success rate in the home aquarium? I’ve heard that once they each a certain size they are more reliant on photosynthesis than being a filter feeder. any truth to this?

    Reply

  149. Casey Whittington says

    Awesome Blog post. In my 10+ yrs of being a Saltwater hobbyist I’ve always had issues with Derasa Clams, I do have 2 currently they have been doing also since I got them over yr ago 🙂

    Reply

  172. chbnorth says

    Great article. I’ll be looking to purchase your derasa as well as squamosa clams in the combing months as the new tank gets started.

    Reply

  177. Meghan Mulkerin says

    I got two clams recently. One died, the other is just fine. It was really frustrating because of course the blue died.

    Reply

  206. ann.wirey1 says

    Great article! Armed with this information, I have determined that although I really wanted a clam, it is not right for me at this time. Perhaps a future goal as I progress through this amazing hobby. Thank you & Happy Holidays!

    Reply

  207. To y says

    I had one of these for about 5 years. I never had to do anything special and it seemed like it was always happy. The whole tank collapsed during a 7 day power outage.

    Reply

  218. Alejandro Rodriguez says

    I didn’t know keeping clams was possible at home. Interesting read. I would need more information. Happy Holidays.

    Reply

  225. Edward Raposo says

    I’ve historically been hesitant to get one of these because of what I thought were extreme lighting requirements. This article is making me reconsider!

    Reply

  243. Bobby says

    I’ve always been afraid to keep clams. If I had a bigger tank I’d give it a go, but I only have 2 32 gallon biocube!

    Reply

  303. Jamie says

    I have just recently bought some Derasa clams and had a little trouble with keeping them looking healthy and good although I knew I was doing everything right. After reading this article I decided to check the quality of my water filter, and it was just not doing the best it could getting rid of all the particles in the water, so I bought and new and better one. My clams so much happier and beautiful, thank you!

    Reply

  304. Doug perry says

    I can’t wait to find a clam that I really like. They are all cool looking but I gotta hold out for that special one

    Reply

  349. Barb Sili says

    >.> Never knew. I’ve never seen any sold in stores. 20 inches is quite large. My tank wouldn’t be able to support a size like that. Atm I’m only into plants.

    Reply

  413. chereecarter says

    Thanks for the article… clams are kind of a final frontier for me and something I’ve never attempted before.

    Reply

  417. Jonathan Dahl says

    Thanks for the great articles. I think adding a clam to my reef will be my next big jump in reefing experience.

    Reply

  433. Chris Peters says

    That clam rock you guys offer in your Derasa clam kit is pretty cool. The best idea I’ve heard of so far is using a shell to mount the clam on to give the foot something to settle on defensively so worms can’t climb in through the hole in the bottom (can’t remember what it’s called, hole will have to do for now lol). The clam rock is a much more elegant solution. Glad I bought a tunze osmolator for the tank I’m setting, never realized they were so central to clam care (not a 100% on getting one yet, but it’s nice to have the option).

    Reply

  444. Nicole says

    Now I am going down the rabbit hole of finding out all the things I didn’t know I needed to know….great info!

    Reply

  475. Jamie Carabin says

    I was happy to see Jake from Reef Builders visit that clam aquaculture facilty in Palau I think. I don’t think the main stress on the population is the aquarium industry…it’s a necessary food source. More aquaculture facilities will hopefully keep the wild population balanced. I’ve always stayed away from clams because they are macro nutrient hogs.

    Reply

  482. COLTON SMOLDT says

    Great reading material would love to have some Derasa Clams that are 2 feet big. Happy holidays and happy claming

    Reply

  500. Kameron H says

    Great read! Currently looking into the diversity of different clam species and which ones would be best for aquaculture based ecosystems and how they would fluctuate with different water parameters etc. it’s crazy how much we’ve advanced with keeping so many different species!

    Reply

  517. Anthony Bloom says

    I have yet to set up a saltwater tank, but would live to throw one of these babies in there ?? great read! Thank you and happy new year!

    Reply

  527. Mike Sloan says

    Been curious about clams. Saw some massive ones at wonders of wildlife, after that I’ve been interested in putting them in my tank. Thanks for for info!

    Reply

  540. Ellery Wong says

    I wonder how many color variants there are? I have the Gold Tiger Stripe and a Purple /Green mantle derasa.

    Reply

  547. Natalie Fernandez says

    Wow great read! I learned lots of useful information. Definitely going and try to keep one of these clams eventually.

    Reply

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