Guys my other goldfish seems to be missing a scale though I can't seem to find out for sure. There is no signs of aggression from the Danios and they all seem fine, no missing scales, not bothering the goldie, etc. There are no sharp plants or ornaments. The ammonia level is fine and he is eating and swimming normally. What could cause this? I am reluctant to isolate him as my quarantine tank is fairly small and has no filtration. Help please?!