Water got between the glass and the paint and created a rorschach worthy mess. I can't live with it. What are viable options instead of black paint on an up and running tank?
Yes, outside. It started at the bulkhead of the overflow. I was putting in a new sump and sure I tweaked the plumbing hard enough to shift that seal in the process.
You can find solid black aquarium backgrounds that may look half decent, though may be a bit of a pain for any option to work around a bunch of bulkheads etc. if you don't have easy access behind the tank.