I know you said you don't want a background, but oceanvisions makes an adhesive vynal background that you cannot tell from a good paint job, and it's much easier to apply/ remove later. They make it in multiple solid colors, no cheesy prints. I use black, I used to use paint and swore by it, but really love the oceanvisions stuff. I really don't know what paint is best, I used good old fashioned interior enamel abck when I was using paint. I never put much thought into it since It was on the outside of the tank, and I was relatively free of funds back then.
dave