I found one at a lake. I have it in a 10gal tank with 4 fish neon sized, a snail colony like no other, and several live plants.
It is doing well and since I have limited the amount of gravel depth I can always follow the trail to know about where it is. I have a 30gal tank of 4 very large gold fish. I am mixing the water so the clam has as mush food as possible. The gold fish are very dirty and the water is perfect for feeding the clam naturally. I can say I would need to add a lot of extra food to the tank for the snails and clam. The extra water from the gold fish allows my snails, shrimp, clam to have a variety of foods an not compete as much. It also helps to clean my goldfish tank water. Clams ae very efficient that way. Essentially, put two smaller clams (1 to 1.5in shell), in a 20gal and try to over feed and maximize the population of smaller, dirty, nonagressive fish. Keep your gravel no deeper than 1.5 times the clam height, throw in a couple of snails, plants, and a shrimp then.....GO! You can watch and follow them. When they feel sage they come up and hang out and just filter away. Better than a whisper 5-15 on a ten gallon tank!