How about we learn from this lesson and establish some productive protocol?
I'm planning to sell my old 50g cube soon. I haven't touched it in over a year and a half. I basically left it empty and let the water evaporate. Originally, I was gonna sell it "as is" all dirty and with sand, but now this makes me want to reevaluate the situation. The tank never leaked when I had it up, but now, who knows? It's been sitting there evaporating for over a year. I don't want to be responsible if it leaks, I'm selling it cheap as it is to get rid of it. Although, if I have to clean it and fill it up with 50g of water during this stupid CA drought restriction time, the price is gonna go up a bit.
There are some things that you just guarantee as a seller of used equipment anymore. I always test used equipment for people because I don't want them complaining to me if they have a problem. But leak testing a tank is a huge pain in the ***, but I guess I'll have to do it.
So maybe, if you're selling a tank, put it outside, fill it with water, and have buyers inspect it?
Maybe we can figure out what to look for? Like dripping seams, wet bottoms, etc.?
I don't know. Just thinking out loud.