it is fine if they look healthyI don't overfeed my fish, but no matter what I do my platys sometimes trail a bit of waste. None of my other fish do this.
I suppose its normal since their poop isn't that heavy to automatically fall down to the bottom. When I first got my angels one of them had a bit of trailing poo but that was because I might have put alittle to much food in because I was afraid the tetras were getting most of the food before they could.What fish are doing this and how long are their poops roughly?
Here is an interesting read on fish poop as an indicator of health.