Ok so I used vinegar to clean the stains just now with a sock on the end of an algae scrubber lol. Yeah I know those were on the outside, but I'm really trying to figure something out like making my own inside the tank background, but just thin and black.
Thanks for your tips bud.
if your going for just a reg plain black background you can buy the premade background
black on one side and blue on other and just stick on the outside. or you can paint it black
or any other color though you would need to take the tank down. another way if you want
it inside it using styrofoam a thin sheet pain it black cure it for 24-72 hours then clear coat
it with clear acrylic or 2 part epoxy. the cheapest method without all the work would be to
just buy the premade reverse-able background and attach it to the outside/back. or you can
go super ghetto and buy a 3 mil black heavy duty trash bag and cut to size and tape it to the
back just like the premade reverse-able background lol.