I am a complete noob to all of this, so please forgive me.
I have a 40g breeder tank that I had purchased several years ago for my turtles. The turtles have moved on to a bigger and better habitat, so we were wanting to set up a simple freshwater aquarium. We purchased a lid for the tank on Saturday. I went to put it on yesterday, only to find out that the tank isn't square. Rather than sitting flush at the corner, one of the end pieces of glass sits in about 1/8 inch, maybe more. I had never noticed in the past because we had never tried to put a lid on it. So my question is, what do I do? Can I pull the sealant off, put it where it belongs, and re-seal it? Or should I try to alter the lid to make it fit? Obviously returning the tank isn't an option at this point since it's so old. I wish I had noticed before now!