That would work if my background was like yours however my background is glued in all the way around other than where my return pipes penetrate.
My tank is acrylic so I can’t see behind it well and no access to the top at all, Only from the side.
I’m Afraid my only solution is to re do it all. It will be worth it in the end.
When you say glued, is it siliconed?, if thats the case you can remove and re-silicone.