Repaired Acrylic Tank

I was offered a large acrylic tank for sale today while meeting someone who was clearing out his goldfish and koi ponds. But I noticed a 3-inch crack on the far back corner the owner had "repaired." He assured me it's fine, holds water, and won't leak... of course. I'm not convinced. This would be one to avoid at all costs, right? As I remember, patched up acrylic means the tank is pretty much trashed.

Okay. There wasn't another piece covering the crack, just a line of what he called "acrylic" over it. I imagine that means he used sealant, but it could have been anything, I suppose. I don't know the guy, so I can't rely on him telling me exactly what he used. He was also playing it down after I was the one who pointed it out.

So.. if there's no other damage to the back panel or underneath it, I could still reinforce that spot myself then? This is located at the bottom of the right panel towards the back, so it's not going to be visible when the tank's in use.

Thanks, guys. That's easy enough.