Hey all ive had these fish around four months the tank is 30 litres ammonia 0 nitrtie 0 nitrate 5.. It was originally only a qt tank but i decided the goldfish in my main tank would probably eat the minnows.... Anyways one of them has never gotten fatter, its so small and im not sure its normal he doesnt seem bothered about food so tired something different which he would grab then spit out!! So going to go buy another different food.today to try everyone else is fine, could he be ill or a runt? Or does he look fine? Thanks!