What is this? clam/mussell?

[jeepsehawk]

About 1-2 inches long, mussel or clam? If I touch it, see movement in shell (retracts), very clear shell. 4 yr nano, 24 gallons and watched it grow for last 3 yrs. Does it mean my tank is healthy having this?

 

[nautical_nathaniel]

Hard to tell from the picture but it looks like some sort of bivalve, also could be an oyster I suppose. Mussels and Oysters generally bind to structure whereas most non-giant clams stick to substrate or bury themselves in it.

 

[jeepsehawk]

I will get better photo tomorrow. My tank, bad husbandry last year but still amazes me, sponge everywhere, multiple bristle starfish and bristleworms. Signs of healthy tank but hardly change water and it is crystal clear. 4 fish are 3.5 yrs old, try adding more and they always die. Bought a 24 dollar urchin, 2 days later I got an empty shell for jewelry. Tank is awesome but will not take anymore wild-life. Think it is at it's limit but very happy taking care of it again.