go to lowes and get some cheap spray paint. i found some on the floor for .99. while youre there pick up some masking tape. go home, tape everything off that you dont want to be black, i cover everyyhint with newspaper to prevent overspray and to use less tape. stand back far enough that it wont run, but not too far or youll be using a ton of paint. wait a while, paint another coat. just keep looking through the tank to see light. its pretty simple and way cheaper than buying background. i actually paid $50 one time to have a tank tinted. i think that was a dumb idea lol