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Freshwater Bivalves

Clams and Mussels

Last Updated: 2/21/12

A clam in my hand on 4/7/10.

Freshwater Bivalves
My Clams
Bivalve Photos
Bivalve Links

Freshwater Bivalves

Clams and mussels are bivalves meaning they have a top and bottom that clamp together. When feeding, they open enough to let water in. When closed, they are a strong fortress that protects them. Animals, including humans, take training and time to break them open to eat.

Clams (Pelecypoda) have two hinged hard plates. Water (with food and oxygen) comes in one opening or siphon and goes out a second siphon (with wastes). A hatchet foot keeps adults anchored in mud or sand. Clam embryos develop inside the clam. The larvae of fresh water clams cling to the gills or fins of fish as parasites. This can harm stressed fish. Freshwater clams are also called mussels.

Clams or mussels are best utilized in large, older ponds to sift algae and other floating life from the water. Place them in a tray of sandy dirt in the bottom. Remove dead ones often so as not to pollute the water. They die if there is not enough food. Dead clams may open up while clams that are tightly closed should be alive. Since clam larvae often parasitize the gills of fish, in large numbers, they may harm fish. Freshwater clam sizes range from 0.3 to 6 inches. Bitterlings from Europe require mussels to spawn.

In a pond situation, large fish, herons, raccoons, and other predators will eat the clams when they stick out their foot. I contained my clams in a cage to protect them.

Clams need tiny suspended foods which is common in ponds but not aquariums. In an aquarium, if you add things like green water (suspended algae) and microorganisms, the filter will remove them and/or the water will foul up pretty bad. An aquarist can target feed them like some people do with marine corals. Basically, you mix up food for them. You can try suspended algae, spirulina, Cyclopeeze, crushed shrimp, Euglena, infusuria, etc. The last two can be bought as cultures mostly used to feed newborn fish fry. Then, turn off the filters in the tank. Suck up a little bit of the food in a pipette or a turkey baster if you cannot get a small pipette. Inject the solution near the clam's mouth (if it is open). Try not to have them close simply by your going in there. A closed clam cannot feed. Squirt some food to the clam every day or so. Turn the filters back on after about 10 minutes. This is how I would guess to feed the clams. There is a link below with a clam food recipe. If you have first-hand experience, let me know so I can add that here.

My Clams

I got my first clams on 4/7/10. I had already had four bitterlings quarantining over the winter and really did not plan to get clams for them but changed my mind. I made a special cage for the six clams. I found a long, curved pond basket with holes. I put in a bag of small aquarium gravel in the bottom. They suggest sand but that would be quite the mess. I set the clams in the basket. I then covered the basket with a piece of vinyl-coated hardware cloth which I had cut to fit. I held it down with six plastic cable ties which can later be cut and replaced when I need to get in to the basket. I deliberately left an opening of about an inch down one end so that the bitterlings can get in there. The bitterlings were still in the basement pond until I dismantled that on 5/5/10. I sunk the basket with the clams in to the 1800 gallon pond. The benefits of the basket included keeping raccoons, larger animals, the koi, and the larger goldfish away from the clams; allowing in small fish, tadpoles, and the bitterlings who use clams to spawn; letting me know where the clams are; allowing me to move them if need be; and allowing flow through of water.

I put the bitterlings, two males and two females, in to the 1800 gallon pond on 5/5/10. I hoped they would find the clams!

On 5/23/10, when I checked on the clams all were shut except for one that was wide open and empty so at least one had died. On 5/30/10, I found two were open. I thought that they are probably all dead. I wondered if putting them in the basket caused the problem because the water flow was not great enough through the basket. Without the basket though, the fish, raccoons, etc. would have eaten the clams even faster.

By 6/13/10, four of the clams were open and dead. I planned to remove the basket the next week to see how the remaining two were doing. I thought they had all died.

On 6/20/10, I took the clam basket out of the pond. I cut open the lid. I tossed the four clams that were open and empty. Two were still shut and gently pulling on them did not open them so they might have still been alive. I stuck them loose in the pond near where the Cyprio filter spilt out. If they were alive, they could move to a location that they liked. The fish, raccoons, heron, or other animals may eat them but I knew if I had left them in the basket, they would have perished. This way they had a slight chance.

The clams never did show signs of life and eventually, I lost track of them. I was not able to keep clams alive in my pond. Perhaps the water was too clear; perhaps the basket did not have enough flow; or perhaps the whole ordeal was just too much for them. I will not get more clams.