Many fish and invertebrates have a specialist diet and they can prove difficult to feed. In tropical marine aquaria the problem that some fish eat exclusively coral polyps is well known and is one example of fishes that should not be sold unless the aquarist can provide the fish with its natural diet. For rockpoolers who catch their own fish he has to find out for himself what they eat. Luckily, many of the rock pool fish will eat anything that is recognisable as food. This may include the aquarist's fingers, but will rarely include 'flake' food that is gobbled up by Goldfish.
Research is paramount.
There is very little scope for 'cheating'. Pipefish vacuum up small crustaceans and larvae in their pipe-like mouths. They have been persuaded to recognise frozen Mysids as food, but cannot be relied upon to do so. The Grey Sea Slug, Aeolidio papillosa , feeding on the Beadlet Anemone Actinia equina . I am interested in all records of Sea Slugs found on the shore or in the shallow sea around Britain.