Is it safe to feed fish earthworms as a main diet? I don't think earthworms is a natural diet of fish in the wild but I have no choice because some of my fish won't eat anything other than earthworms like my tiretrack eel, leopard bush fish and flowerhorn they also do take bloodworms but it is usually out of stock in my petshops so I feed them earthworms that are fed on chicken manure and kitchen scraps. My fish seems healthy and has voracious appetite on the worms but I don't know if its fine for it to become their main diet forever.