I had a thrid purple for about a month while a local was moving. They just all get along. Food - room - hiding places. Most people forget about the food, but they need to eat to feel secure too... eat enough to grow about 1" or more per year.
I have had the hippo since it was less than an inch.
Tangs get a bad rap about being disease magnets, when they are really just more sensitive to the stupid things that their captors do. It is the fault of the people not the fish. Find a good wholesaler for a good LFS and do a good job yourself and the tangs will rarely, if ever, show signs of disease. Some of the time, the wholesaler or LFS has done the damage and they issue just comes to the forefront in your tank weeks later.
BTW - My chocolate is my favorite too.