Agree with Krich, except I'd add any non-live (frozen or freeze-dried) bloodworms or brine shrimp, etc. to the list.
They are animals. They know how to forage for feed. If they are not doing it yet, they have no appetite either because they are still adjusting to the new tank and water or they are under some other stress. They should start feeding in the first week if all is good. 1" indeed is tiny, I'd be worried about them not feeding too.
Perhaps they improved or changed the way they make canister filters now but when I used to use them, there should have been a minimum of a drop in the water level between the tank and the canister. IDK how well yours will be functioning standing on the same level and your stock pond.