You can also get the frozen green mussels on the half shell at the Asian market.
Copperbands & Moorish Idols love them, just dont try it if you want to keep Clams.
Also look for frozen "Smelt Egg" It is yummy for both humans & fish alike.
If you can get "Japanese Mayo, Green Mussels, & Smelt Egg" let me know & I'll give you a wicked recipe where the ingredients help the tank as well.
Stu