Here is some basic info on Oysters just for an overview.
The Eastern Oyster
(Crassostrea virginica)
Range:
Along the coast of North America from the Gulf of the St. Lawrence to the Gulf of Mexico. It has also been introduced to Hawaii, the West Coast of North America, and other locations worldwide.
Oysters are typically found in estuaries, sounds and bays, from brackish water to very salty lagoons. They are very tolerant organisms, being able to withstand wide variations in temperature, salinity, suspended sediments, and dissolved oxygen. In the Bay, oysters are usually found in areas that have over 5ppt salinity.
Feeding:
Oyster are filter-feeders, drawing water in over it's gills through the beating of cillia. Suspended food (plankton) and particles are trapped in the mucus of the gills and transported to the mouth, where they will be eaten, digested and expelled as feces or expelled (spit out) as pseudo-feces. Feeding activity is greatest in oysters when water temperatures are above 50°F (~10°C).
Reproduction:
Oysters spawn when water temperatures become greater than 68°F (~20°C). They are broadcast spawners, releasing eggs and sperm into the water column. Fertilized eggs develop into a planktonic or swimming larval form. After about two weeks these larvae will "set", a process of cementing themselves to a hard substrate, and metamorphose. This newly attached oyster is known as a "spat".
I'm not sure how much of a problem they would be in destroying any amount of plankton in a tank and would maybe be concerned with the spats growing in the display tank.
