Are Giant Clams Reef Safe?

Giant clams are one of the most gorgeous and interesting creatures in our hobby! In this article, we will explain why Tridacnid clams are reef safe and how to decide if a giant clam is a good choice for your reef tank.

Clams of the Tridacnid family are absolutely reef safe! However, giant clams may not be good candidates for all reef tanks. There are several factors to consider if a giant clam is a good addition.

Reef keepers should take into account the size, maturity, and stability of the reef tank. There is also the issue of predatory invertebrates and fish. Some crabs, starfish, and triggerfish have been known to eat giant clams. We also want to look at our lighting and filtration equipment.

What Kind of Clam Will Do Best?

There are four members of the Tridacna clams that are common in the reef keeping hobby. They all have similar care requirements, but some are easier to keep than others. Tridacnids have the same biology and rely on zooxanthellae within their mantles as well as filter feeding. Almost everyone has been stopped in their tracks at the sight of the Tridacnid mantle! Many would be surprised to know that the fleshy and gorgeous mantle is hard at work producing nutrition for the animal.

The crocea clam is a beautiful and colorful clam also called a Boring Clam. Crocea gets this name as its natural behavior is to burrow itself between pieces of rock. Once it has attached itself to the rock, crocea clams will rapidly open and close its shell. This motion, in conjunction with the low profile scutes, actually bores into the rock. It also secretes an acid to soften the calcium carbonate in the rock! Fully grown crocea clams will measure about six inches in length.

Derasa clams are probably the easiest to keep out of all the Tridacnids. They can grow up to be giants, maxing out at around 24 inches! They do not tend to grow quite that large in average-sized home aquariums. However, they are very fast growers and have been known to triple in size in just one year. As they begin to mature, they will rely mostly on their own zooxanthellae for nutrition. A smaller derasa will need to receive regular feedings of phytoplankton if it is in a nutrient-poor reef tank.

The maxima clams are the hobby’s most popular tridacnids. Maxima’s have beautiful marbled and spotted patterns on their mantles. While they are one of the most gorgeous, maxima clams are not the easiest to keep. They are a little more demanding of placement and water flow. Maxima clams grow to be about eight inches at maturity.

Squamosa clams are one of the larger tridacnids. They can reach about eighteen inches in size. They are similar to derasa clams in terms of care. Squamosa clams are not as demanding with their lighting requirements. They are also not picky about the substrate. Squamosa have higher profile scutes on their shells. The mantles are generally neutral in coloration. Most are brown, tan, or yellow color with sparkling gold accents. However, the rarest squamosa color variants are blue-green and solid blue.

Are Clams hard to keep in a reef tank?

It is true that tridacnid clams are somewhat difficult to keep in captivity. Although, it is not impossible for tridacna clams to thrive in novice reefers’ care! For the reef keeper who is willing to put in the work, diligence will pay off. The two biggest challenges are maintaining the proper water parameters and adequate lighting. These invertebrates do have specific nutrient requirements that may be hard to retain. Nitrate is the most crucial for reef keepers. Many SPS collectors will aim for nitrate levels to be close to zero. However, nitrates at a range of 2 – 20 PPM are vital for keeping tridacna healthy. Clams will also draw calcium and alkalinity at a faster rate than corals. It is recommended that these levels are monitored closely. Automatic dosers should be properly calibrated and set to keep up with the tridacnids’ demands.

Tridacnids are also filter feeders with a complete digestive system. They use their inlet siphon to draw water in through the mantle. Tridacnids have organs called ctenidial food grooves or gills. The gills filter out the particulates. Nutrients then travel from the stomach to the intestine. At last, the waste is excreted through the excurrent siphon. In a well-stocked reef tank, there should be sufficient nutrients for mature clams. However, small clams or those in nutrient-poor reef tanks should be fed live phytoplankton. A clam can starve to death in a very short time. That is why we recommend regular feedings of OceanMagik.

Providing adequate lighting is the second most crucial component to keeping giant clams. Like most zooxanthellates, clams will need a period to adjust to changes in lighting. When clams are young and under two inches, they cannot tolerate intense lighting. Small clams and new clams should be placed low in the aquarium.

The ideal PAR will be somewhere between 250-500. However, depending on the nutrient level of the reef tank system that number could be higher or lower. Some have even had success keeping tridacnids at over 700 PAR. Remember, these beautiful creatures are sensitive to changes in lighting. The best course of action is very slow acclimation. Make tiny adjustments to the light intensity every 7-14 days.

Conclusion

To sum, giant clams are absolutely reef safe, but they do require diligent care.  We have gone over a few of the most crucial factors in deciding if a tridacnid clam is a good choice for the reef tank. AlgaeBarn always recommends regular live phytoplankton feedings in reef tank systems. Although it is especially recommended when tridacna are in the system.

We know more about the feeding behaviors of giant clams than ever before. Also, advances in aquaculture and mariculture practices have improved dramatically over the years. Thankfully, these gorgeous creatures will continue to be sustainably harvested for the hobby.