I also buy frozen fish fillets for my cat, cover them with a little water, but NO CLING FILM ... not in the microwave ... or plastic for that matter. Apparently there is an agent in the plastic when it comes in contact with heat, it becomes cancerous (dont want to worry you, sorry) So I always use a Pyrex or glass dish with a glass lid in the microwave. We dont want anything happening to the cat ! (Or you for that matter !). My cat also likes raw mince, or lightly cooked mince, in fact any meat leftovers, and of course white fish leftovers , unless it has been cooked with garlic ! He doesnt like salmon though, only white fish .. fussy cat. They also like a tin of tuna sometimes, pilchards, etc. I dont like giving my cat too much tinned cat food .. I prefer something natural, so you know what you are giving him. Good luck !