Well, I have been looking in the wrong places for my pet mussels......
They are far from unknown as pets in tanks and ponds.
This is a cute article.
Fresh Water Mussels - Better than a Rock By Robin Engelking
As published in Aqua News, Minnesota Aquarium Society, July/August 1999.
Aquarticles
http://www.aquarticles.com/articles/...20Mussels.html