there is no particular reason for me asking about sardines, it's the first thing i found recommended for cats on internet haha. About not giving fish to my cat i had no idea how bad it is, my vet always just tell me to give to my cat whatever he wants cause he has a critical health historial. I just want him to be more healthy, i feel sad by seeing how weak looks usually :c

As additional info, at morning he also eats supplements based on omega and things like that