Planted Tank Enthusiast
Join Date: Jan 2013
Location: Baton Rouge, LA
I don't know what size tank your talking, wicca, but if on the smaller size, I would remove the paint and start over. Get a few different colored scrapbook colors, hold behind the tank filled with water, and see what looks best to you. Then repaint, or use paper. You can always change paper, but not so easy to change paint.
You are right, black on black or dark colored background will not show up nicely, especially with dark substrate. I recently just taped plain white copy paper behind a 5 gallon Rorschach guppy breeding tank because they did not show up well on clear glass, even with light colored paint behind it (creme colored). Now every little fry pops and stands out. I don't want to paint the tank because I may not always have blackish fish in it.