I'd be really careful about putting any paint into your tank. Even Krylon Fusion could cause issues if anything goes wrong [paint starts chipping, leaches any chemicals long-term]
with that said, I painted some PVC with Krylon Fusion and had it in my tank as a return from the sump on my last setup, and everything was okay for the 9 months or so I had it set up.
Make sure to give the paint plenty of time to cure/set after spraying, before exposing it to the salt. IMO frag racks are not the best choice for using paint on in an aquarium