Hi Paul, Adult brine shrimp, which approach a half inch in length, are far too large to be ingested by filter feeders. Actually, brine shrimp themselves are filter feeders, and the particle size they are capable of ingesting is probably about the same size most bivalves would be capable of handling. If you wanted to go to the trouble of buying dried brine shrimp eggs and hatching them, the newly hatched larvae, which are about 0.4 mm in length, might be suitable as food for bivalves. But they grow rapidly, and within a couple of days would certainly be too large. Pectens don't require animal food, as far as I know, and I think it might be easier to sustain them with a diet of algae. Paul M.