When the purple tangs are stocked at the big wholesalers they are kept in tiny cubes. The fish don't do well and they break out with HLLE very quickly.
I've found that these fish turn right back around very quickly. In my outside refugium tank lit with just sunlight they HLLE heals up in less than a week.
In my display tank (same water) with artificial light and feeding just Romaine lettuce in a community tank with lots of other tangs it takes about two weeks or so for the lateral line to clear up.
They are super hardy fish. As great looking as they are in the aquarium, outside in the sunlight their colors are stunning.
Dave B
Holy smokes, you're still around!? It's been a while, I hope all is well your way!