I really like the blue over the Powder blue, and I was planning on getting a small young one.
I went out today to get pricing on a Larger tank, right now, I'm looking at getting an acrylic tank around 140Gal to 150Gal 6 ft long. Probably not til spring/summer next year, plus whatever time it takes for me to build it into a wall in my house...
So, I should be safe with a Blue tang in my existing 4ft 90Gal, as long as i get a small one?