Opinions on this situation?

[snakers55]

Hey everyone, I've run into a situation and I'm not exactly sure what I should do about it. I sold a friend of mine's cousin a 100 gallon aquarium that I had been using for over 2 years for aquatic turtles, so it was right full of water for that time, until about 2 months ago when I put the aquatics into something else and put box turtles in it.. I'm not working at the moment and have no income, so I needed some money for christmas presents and decided to sell the tank. My friend has seen pretty well everything I've ever done with this aquarium so he knows very well that it held water no problem. Monday night, his cousin came and picked up the tank for $100 (which is about 1/4 the cost of a new one) and tuesday night I get an email saying he tried to fill the tank, it leaked out everywhere after about the half point mark... I have overflowed this tank in my house a couple of times, so I know that it didn't leak past the half point mark for me.. Also in the email, he says that the cousin resiliconed it, so he's tampered with it right there, and it still leaked (so he did a poor job). Now, he is asking to return it and get his money back, which I have already spent on a present for my girlfriend for christmas, and this leaves me with a ruined tank with a poor silicone job... What would you guys do in this situation?? I highly doubt that in about 2 months since it held water, and then moving it up the stairs and onto my deck would cause any leaks.. The whole aquarium was resiliconed about 3 years ago as well by the person I bought it from.. The only other thing is that my friend owes e $50 that I loaned him about a month ago which I really need back for christmas presents and to buy food for my herps.. This wouldn't be as big of a deal if I had any sort of income, but I don't.. The only way I can get his money back is to sell off something else which I don't want to do.. If it were me that had purchased the tank, I would have just counted my losses or maybe spent a little more time resiliconing it.. If anyone bought an aquarium from a store that had a leak in it, resiliconed it, still leaked and they tried to return it to the store, they'd be told to get lost am I wrong?? Any suggestions welcomed.. I also might add that the buyer is well into his thirties and I'm 18 if that makes any difference.. I'm not trying to rip him off or anything, but I also don't want to be ripped off myself..

Thanks for taking the time to read.