If its convenient to your setup, put a sheet of black kydex back there, held with small magnets. Then just every so often pull it out and soak it in a tray of acid.
But for the back wall of my tank I use a long handled scraper. Black back doesn't show buildup very much so sometimes it gets a little out of hand before I get to it.
When mine got bad I scraped everything off, now I have a stick with replaceable heads, one being a scraper and the other a pivoting sponge, I just clean it every couple of days, takes seconds. I also increased my flow just a bit.
Although I like the look of a clean black glass on the back to really make colors stand out, to try something different, I recently glued a small piece of that on my back glass. I'm hoping it will grow all the way across.
It has a half inch of growth on it, I just have an algae trough at the surface of the back of the tank and it blocks the light from going there, which I like
I have never cleaned my back glass since setting up my latest tank 11 months ago, When I bought the tank it already had a black back glass not that you can see much of it anyway. You can just see a little coralline algae top right on the weir developing.
Wanted to pump this up. I too really like the back wall but it is hard for me to keep my overflows clean, they seem to cover a lot faster with coralline and are A LOT harder to get clean too. The glass back is really easy with a scraper but the overflow boxes are what I am having problems with.
I am hoping someone has some suggestions on how to get mine clean first and then how do you keep it clean? If I only had one overflow box I would let it go natural but I have two so I want them to stay black and clean. Looking forward to the suggestions