Well this may end up being the shortest lived tank setup I've ever had.
I'm not sure if this is a scratch that I hadn't noticed before, or if it's a crack that has appeared today. It runs 3/4 the length of the tank smack in the centre of the rear panel. I can't get a close enough look at it. I cannot feel anything with my finger. Where I've circled the line, there is a discontinuity that makes me *very* concerned that this is a crack and not a scratch.
I don't know what to do.
For now I've marked the end of the scratch line. If it grows, then I know it's a disaster waiting to happen. If it doesn't .... well then I'm still not sure what to do.