I have a 55 gallon tank with 6 clown loaches, 2 yo-yos, 1 botia robusta, 11 cardinals, 3 siamese flying foxes, and 1 large plecostomus. I have had cases of fish tuberculosis in the past--I had a couple of the affected fish dianosed at my favorite fish store (Preuss in Lansing) under a microscope. I was told there was nothing to do for the disease and that once it was in my tank it would remain there forever (or I assume the tank would be a carrier--unless I tore down everything, bleached it all, and re-stocked with brand new fish). So--I try to keep the water as "healthy" as possible to prevent any stress on any fish and reduce the chance that anyone comes down with the tuberculosis.
The cardinals were the last to be added at least couple of years ago.
I have had these clowns for a few years--4,5 maybe more. I have had the yo-yos longer, and the botia robusta much longer.
My problem is that one of the clowns just hasn't grown as fast as the others--I got them all from the same store within 2 weeks of each other. He has grown--but just not as much as the others. Now I am beginning to think that he has this "skinny disease" that I read about in this forum. He is still eating and swimming around. But--it seems like his bones are beginning to show. I will attach pictures.

Him alone.

Him with his siblings to compare size.
Through the years, I have always noticed that he was different from the rest because one of his stripes doesn't go completely around him. The other fish aren't mean to him--he is just not always the first fish picked to play team games if you know what I mean.
What I need help with is--- do I set up a hospital tank just for this guy? or do I treat the entire tank? Do I need a full 10 gallons for him or can I fill the tank part way (I have an empty cracked tank)? I am assuming that Levamisole is the recommended treatment. I will have to find out if I can even get that--and make the drive. Maybe my local Tractor Supply has this in a mammal (farm animal) form--could I use this? What do I look for? And I need to know everything about how to treat and change water -- etc. I did read over Shari's article--but my head is spinning--too much brain power is needed for my real job and my kids.
Of course--all of this is assuming that anyone thinks that this fish has the skinny disease. All the fish started at the same size but he just hasn't grown as fast--but he still eats.
Thanks and sorry to ask a redundant question.