I don't know if anybody has ever done this to black-out their tank for algae control or whatever but…
I used to try to cover my tank with towels or put cardboard over the glass. Both ways are a pain & don't work that well. I've found the easiest way is to use aluminum foil. Zero light passes through it & it conforms to all bends around the tank. Just tape the ends. It's easy to do. My DIY tip.
I used to try to cover my tank with towels or put cardboard over the glass. Both ways are a pain & don't work that well. I've found the easiest way is to use aluminum foil. Zero light passes through it & it conforms to all bends around the tank. Just tape the ends. It's easy to do. My DIY tip.