2014-05-16 Species Spotlight- Derasa

This is the third Derasa clam I've kept in my personal aquarium.
My first clam came as a birthday present, a 5" derasa, had the tiger spotted marking.
Second one is similar to the one below, also a 5" derasa, with a slightly lighter color. That one unfortunately died due to disease introduced by another clam.

The current clam I have is between 8-9" and has beautiful stripes down its mantle.

In many people's opinion, Derasa clam is one of the hardiest, and easiest clams to keep.

In my opinion, squamosa is the hardiest and easiest, but Derasa clam is a close second.

Like all clams, it does require full reef water condition with extra care in calcium level for proper growth. It will also need slightly nutrient rich water (i.e. plenty of fish waste) to thrive as it absorbs phosphorous from water to build its body parts. Hence it's nearly impossible to keep clams in an aquarium with no fish in it.

Although Derasa doesn't require as much intensity in light as Maxima and Crocea do, it still need a decent light source. I've been able to keep it healthy under power compact at at least 5W/gallon with slower growth. Currently I have it under my AI sol blue LED fixture at around 70% at peak time and it's growing rapidly. Many others keep it under Metal Halide, which is more than enough light but can really suck up your energy bill.

Unlike Maxima and Crocea, you should place this clam on a sand bed. And give it plenty of room to "rotate" as it has a mind of its own in choosing what direction it wants to face. Lastly, keep the tank free of potential clam eaters. I had a flame angel who would nip at my Squamosa before. That flame took its own life one day, and my flame angel II has been very well fed and has not touched the clam.

One other conscience complier is that most of these clams you find in the trade are now aquacultures with minimum to none impact to the reef. And the bonus of aquacultured livestock is they are far hardier than those wild collected.

Maxima clam pinched mantle

Very Sad Story, My Tahitian Maxima clam suffered what many hobbyists refer to as "Pinched Mantle" syndrom. The "pinched mantle" is caused by a protozoa infection, similar to that of the malaria type for human infection. This type of infection is widely spread amongst Maxima and Crocea clams, and has recently spread towards other Tridacna clams such as Derasa and Squamosa.

After doing lots of research, I decided to perform the freshwater dip (FD) treatment. The principle of freshwater dip is to kill invertebrates and bacteria cells by osmosis while the water finds equilibrium between brime and fresh. The Tridacna clam is actually surprisingly hardy when completely submerged under the freshwater. The key is the water must be of the same temperature and of the same pH level as the home aquarium. The photo above is my clam being soaked in freshwater for 30 minutes.

The photo above shows the pinch of the clam prior to the dip. You can see the second scute of the left mantle is slightly shrank. It is better to detect the distress and treat it while the clam is still strong and relatively healthy versus making the very invasive freshwater dip during its latter stage.

This photo shows the clam an hour after the dip. The clam is obviously distressed and is gasping for both the "right water" and fresh oxygen. The clam remained in this stage for the remainder of the day without much change. I will post follow up article if the clam's condition worsen or improves.