Also try cut pieces of Shrimp. My Del loves that I had 2 Dels before. For some reason, I have had a hard time keeping more than one Poly. One always seems to develop health issues while all the other fish remain healthy Anyways...just try a variety. You should be able to find something.
you could try brine shrimp, but if you just got him i would wait a couple of days. he may just need to acclamate to the tank. hate for you to waste money on all different kinds of foods if you dont need to