so I'm sure I'll be arrested for this one, I had a very small yellow tang in my 29 who grew to a fat happy yellow that I took to Phenomenal cause he outgrew my tank. I'm not saying house tangs in small tanks, but I think it's more about keeping them healty and happy. I'm sure temporarily housing them in a smaller tank won't cause huges issues. They do come from the ocean and that's a pretty big tank.