This effect from the blue is caused by a type of crystal that the fish incorporate into their coloration the name of which eludes me at the moment. It is quite common in reef fish however, almost difficult to avoid. many of the angels have some of it, especially as outlines on the fins like on your yellowpeel. My Majestic angel has it, Annularis angels do, Niger triggers, Koran angels, etc. Like I said, it's easy to find, and the right lighting makes it beautiful. I find actual sunlight coming in a window gives the best effect. Then there are a few red/orange fish that glow somewhat as well, from a different cause. Flame angels and flame hawkfish being the easiest examples to think of.