Hello,
I use the seaview stuff on my background, it works well for a few months but then once it dries out from the neat from the tank the backing will start to come away from the glass.
Then its just a case of adding more seaview to stick the background back to the glass. If I could get to the back of my tank I would remove the backing and paint it black. This is what I will be doing in the near future when the tank has to be moved for a new carpet to be fitted.
Are you going to be adding plants to your tank? if so painting the back black is the best way to go.
I only wish I did it with my tank before it was set up.