I still think $20k is far too much. If I can claim $20k, I will happily break my tank and set up a new one with that $20k.
Not sure whether Qianhu really advised the couple that the tank they sold them was suitable for marine use. My instinct is that the tank is bought off shelf and not custom made. And most tanks that are available off-shelf are not really suitable for marine use. Did the couple actually asked Qianhu if the tank was suitable for marine use? If they didn't ask.... how can the blame the company. If Qianhu did tell them that the tank is safe for marine usage... then I would think that Qianhu is at fault. But as most reefers as said, most likely they would pay the cost of the tank only.
Anyway, I don't see any reasons for us to defend the tank makers. If it's their fault, we will sure whack them. Just like Atlantis. But everyone can see clearly from the report that this couple just want to make a quick buck out of the situation.