I haven't seen any tanks with mussels that I am aware of. I confess I thought mussels were freshwater. I have used cleaner clams, conchs, all kinds of snails and crabs, and starfish in an effort to keep my tank clean. I haven't tried mussels tho. Sounds like they would work well in a refugium or possibly a sump. BTW, the picture you reffered to is not there.