I have a 90l tank with 6 danio and 7 minnow. It's been going for over a year now. A while ago one of the minnow became very thin and had a curved spine so I put it to sleep with clove oil (thanks to advice on here) Since then two of the other minnow have looked to be going the same way. But it's been a few months and they are still alive. They look miserable and very thin. They hang around at the back corner of the tank and don't seem to eat (although surely they must be eating something to still be alive?)
The danio all look very healthy. As do the other minnow - some of those look pretty podgy to be honest.
I'm just not sure what to do with the sad minnow. Are they just suffering? Would it be kinder to put those to sleep too?