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Freshwater Clam Problems

The aquarium store called it a “shark tooth clam.” I was wondering if I could place it in my freshwater 20-gallon tank.

By Mike Wickham

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Q. I found a lovely clam at a store near my home. Unfortunately, I couldn’t find a staff member that knew any information about this clam. They called it a “shark tooth clam.” I was wondering if I could place it in my freshwater 20-gallon aquarium. In this aquarium, I have dwarf gouramis, neon tetras and angelfish. The aquarium base floor is small river pebbles, plastic plants, driftwood and a plastic hut. Could you tell me if this clam will survive in my aquarium? Any care and feeding information would be appreciated.
Theresa Scott
Mississauga, Ontario, Canada

Click image to enlarge
Clams have trouble living in aquarium water because it's so clean
In nature, there are plenty of materials for clams to feed on; in an aquarium’s clean water, however, they will easily starve. These are freshwater clams belonging to the genus Corbicula. Photo by Oliver Lucanus.

A. I was unable to positively identify the animal in question, as I could not locate a scientific name for it. I managed to find one person posting forum messages selling them on the Internet, but he did not respond to my attempts to contact him. One of his ads did, however, contain photos, and these photos lead me to believe that this clam is one of the winged oysters (Pteria spp.). As far as I can tell, these are all marine species — though that doesn’t mean they could not survive for a time in freshwater systems. Many species live in coastal areas where the salinity changes often.

In any case, buying clams for your aquarium is a bad idea. Even if we were to assume that these “shark tooth clams” (the shell is shaped very much like a shark’s tooth) are truly freshwater clams, they don’t have much chance of survival in an aquarium. Clams are filter-feeders that pump water in and out, and filter out the particulates in it for food. In the wild, there are a lot of microorganisms and detritus in the water, and clams live “happy as clams” on it; but in the aquarium, they starve. The water is just too clean for them.

There are other issues with keeping clams. One is that they dig. Some will dig out of sight within moments of being placed into your aquarium — never to be seen again. How much fun is that? A forum message regarding these “shark tooth clams” said that they were 5 to 6 inches in length. If you had live aquatic plants, a clam that large probably won’t dig out of sight, but it will uproot your plants as it crawls around.

Another possible issue is reproduction. In the forum ad message I mentioned, the poster claimed that the “clams are hardy and can reproduce rapidly.” This sent up a red flag for me because I have never heard of any bivalve mollusk reproducing rapidly in a freshwater aquarium — or reproducing at all. If this “clam” is actually a freshwater mussel, its larvae, called glochidia (glock-ID-ee-uh), are parasitic on fish. They attach to the gills and skin. Fortunately, glochidia usually do no damage to the fish, and many require specific fish species to act as a host. Still, if this animal reproduces rapidly as stated, it may clog the gills of your fish.

There is one more issue with keeping clams or mussels in your aquarium. They need plenty of calcium to build their shells. Your water may not be hard enough for them to do so. The shell will soon become pitted and discolored as it dissolves away. This is obviously bad for the clam.

Anyway, though I was unable to identify the particular species of the “shark tooth clam,” I highly recommend that you avoid keeping clams in your aquarium; they are destined to starve. Some people have success with clams in ponds. The water there is usually substantially dirtier and full of microorganisms. But there should be substrate so that the clams (I use this word in a generic sense that includes mussels) can dig safely away from any fish that might hound them.

If anyone has any further information on “shark tooth clams” (particularly a scientific name), please pass it on to me for a possible future update in this column.

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