White stuff on angel fish??

And has apparently.
Watanabe's angelfish feeds primarily on zooplankton. This feeding habit makes it less “rock-bound” than most other species of angelfish and you can often see it swimming around in mid-water in the aquarium. It is a powerful swimmer and should only be kept in aquariums with plenty of swimming room. Keeping it in an aquarium smaller than 100 gallons is not recommended. The aquarium must also be large enough to accommodate suitable hiding spots. When newly introduced to an aquarium, Watanabe's angelfish is normally quite shy and will spend a lot of time hidden, but it will gradually become bolder and bolder as it gets used to its new home and eventually adopt a more pelagic living style.I realise these live in harems in the ocean but in a small aquarium like the O.P. has even one would be pushing it IMO.