Advice Feeding fresh clams

[Reesj]

I'm quite new to feeding anything except pellets. I got my 180 gallon going for starters with few banner fish and hoping to add some butterfly and angles in few days.

I bought about 20 fresh clams from a chineese shop as I heard fish love them. They were in ice cold water and they gave me dipped in them. I came and put 2 in to the tank and rest to the sump.
My problem is that they are closed off. Do I need to freeze them or open them for the fish?
If I leave them in tank for a while will they open up and not die off and pollute the water ?

 

[Subsea]

Normally, when I buy buy clams, oysters or mussels, they are refrigerated & dry. When I am ready to feed, I remove the live bi=valve from the refrigerator, open shell and dissect flesh to feed fish. One week is maximum time in refrigerator. When I buy a small sack, I refrigerate what will be eaten in a week and I freeze the rest.