Painting the back wall...

[Tobman]

I used something like the Krylon Fusion Black and then spray painted polyurethane on top of that. to make sure it was waterproof. Just make sure the paint you get says it will adhere to glass.

 

[demonsp]

I used Spray paint color was pacific blue , i bought can from lowe's. I needed about 1 can and a 1/2 to paint back of a 75 gal. I was very pleased with the outcome.

http://reefcentral.com/gallery/data/500/129799mini-DSC01177.JPG

 

[badgers034]

I used Rust-o-leum for outdoor furniture. I figure that if its good enough to withstand weather, I am sure it can take the little beating my tank gets.

 

[bower23]

Go to Lowe's and get some thin acrylic sheets. Paint them, tint them, or whatever and use that on the back of your tank. That way you can remove it or change the color without messing with the tank. That's what I'm going to do on my next tank.

 

[reefnetworth]

if your set on painting may i offer some friendly advice? Porter Paints or Pittsburgh Paint carries "Marine Paint". it is a medium blue and its reef-safe! it's a little more expensive, but you have no worries of leaching, chipping, etc. and it looks as good as the blue acrylic sheet. have a great day

 

[The0wn4g3]

Hit up Lowe's or The Home Depot for some black (flat or glossy) latex paint. Comes in a little round can. Use a medium sized brush and put 1-2 coats on the back. Since it's on the back, you don't need to worry about globbing, just make sure it runs. Just paint it on as thick as you want.
Should dry in a few hours and you'll be set.