So I'm rehabbing a used 125 gallon tank in my friends basement. He himself is the owner of a 180 gallon acrylic tank and several other decent size African cichlid tanks, and he has been helping me get my tank together. Long story short, the other day I walked in while he was scrubbing down the inside of the tank with hot SOAPY water. He used dawn dish soap on my tank, and insists he has done this many times without ill effects on his fish. He also started using goo-gone and paint thinner while removing one of the seals. I am horrified because everything I've read about cleaning old tanks states to NEVER EVER EVER use household chemicals or soaps to clean a tank. My question is, what do I do next? Is there anything I can use that will neutralize everything he threw in there? Do I just rinse rinse rinse and then rinse some more? Or do I just need a new tank? I find it hard to believe that he has done this many times as he says, but his aquariums are healthy. What do I do?