I know when it comes to using actual fish (or fish flesh) to feed your fish, you should avoid using fish from different climates as feeders for other types of fish, i.e. avoid feeding coldwater fish to tropical fish, and avoid feeding freshwater fish to saltwater fish, etc.
Does this apply to inverts? I ask because I picked up some frozen krill as a supplement to my Jack Dempsey's diverse diet. He eats any sort of prepared food I feed him, including shrimp pellets, algae wafers, betta pellets (only did this once just to see if he liked them), flakes, sticks and sinking crumbles. His staple diet is Omega One Cichlid Pellets. He also loves frozen brine shrimp, frozen bloodworms, frozen tubifex, live blackworms, live snails, algae I scrape off his walls, pretty much any type of veggie, any sort of live insect (i.e. feeder crickets) and live guppies (home-bred). So, although he gets a really diverse, healthy diet, I thought I'd change his frozen menu a bit. He's getting bigger, and it seems wasteful to feed him stuff like brine shrimp and bloodworms since he eats almost as much in one meal as all of my other fish combined. Krill are pretty big so they seemed like a good step up. Is it safe for him to eat them, or should I worry about the nutrition being off because they're from the ocean? I also fed some smaller krill to my golden wonder killifish and some chopped up pieces to my kribensis and ram - they seemed to like it, too.