I saw it today, and it has numerous bites on its tail fin. The other loaches must be causing this? They are too small to have been caused by anything else. I have no idea if it even has skinny disease. It seemed healthy and fat when I bought it, and the thinness now could easily be due to the others not letting it eat. I am going to take it out and QT it in a 10 gallon. Anything I should add? Salt? Raised temperature? And even if it does heal, what is going to happen when I put it back in the 75?