What Oysters to buy?

I'm looking to DIY/make a liquid concoction of oysters to feed my corals at night with the return pump off. I have a commercial-grade blender that will liquify anything you drop in there. I want my end-product to be a thick liquid that will suspend in the water overnight with only an internal PH moving water around with the coral tentacles feeding like crazy overnight.

QUESTION: So if I buy fresh oysters from my local grocery store deli (and I'm willing to take the time to crack-open fresh oysters).... what name of oyster should I look to buy? I many times see several different types of oysters available on ice.

Oyster experts please help me on what oysters to buy.