Nope... I did the same thing on a couple of my tanks. I painted the back black, then realized the whitish clear intake looked horrible. Painted them, can't even hardly see them now. Krylon is the only thing I'd use, so looks like you're covered. Since my tank was running, I just used the intake off a spare
AC I had sitting around, let it cure, then changed them out.
If you haven't purchased the paint yet... I'd go for gloss over flat. Since the glass has a glossy look, the flat might stand out a bit more than the gloss does.