When painting an aquarium, be sure to tape off the areas you don’t want paint on. This is especially true if you are using spray paint. The wind will catch the paint and cause some of it to get on an area you don’t want painted. If this happens on a glass tank, simply remove the dried paint with a razor blade or some sort of paint thinner. Acrylic is a little more difficult though. It can be buffed out with a mild liquid abrasive and a buffing pad, but don’t use chemicals as it can damage the acrylic.