Personally, I paint the back with Plascon Glatex-8 two-part epoxy paint. It is expensive though.
is this inside? i think its overkill, personally i use plascon G116 midnight blue in a super universal enamel (+-R45 for 1lt you only need 250ml), you can have the same thing mixed in velvaglo if you wanted a better quality... remember your paint will only be as good as the surface you put it onto so wipe with methelayted spirits with a clean cloth..
oh and glatex (boats) and 2k (generally for cars) are the same thing.. glatex being more expensive.... they have just awarded a branded name for 2k for boat use...
what makes you think i work with paint!!!
last comment: if you are in a hurry to position your tank get paint mixed in a QD ( quick dry) enamel in the colour of your choice it dries within about 15-20min or even less on warmer days... i find this adheres to glass better if the glass pane is slightly warmed prior to painting...
just my 2c
Might be a dumb question but can I put plascon on with the tank full? My nano has no background with a window behind it and I wanna paint it.