For me the type of paint isn't critical but a coat of epoxy over the paint is, it protects it and will seal it, making it aquarium safe. I used standard cheap spray paint on a few projects, covered with bondo epoxy fiberglass resin, a couple layers of it. some projects ive painted end up getting a layer of algea on anyway, so you couldnt even realy tell i painted them, i like earthtones, greys and browns