This is what I get for always thinking that people are 'good'
Have you tried contacting Aquabid? If not, I would definitely contact them and explain the situation to them. Even though you didn't purchase the fish through them, you did find the seller through them so maybe there is something they can do. If nothing else, maybe they could suspend his account so that he isn't able to do this to anyone else until you get your fish.
I wonder if the reason that he is doing this to you is because you emailed him privately and didn't order through Aquabid. He is able to screw you out of the fish, and you aren't able to leave any feedback about it
I don't know which bank you use, but I use Fifth Third and about 6 months ago I ordered a monthly planner from a company, and they took $26 out of my checking that day. The next day I got an email from the company saying that they didn't have any in stock, and asking what I wanted to do. I emailed them repeatedly and called them for a few weeks, telling them that I just wanted my money back and they never replied. I took my statement to the bank roughly 2 months later, and the bank didn't even ask questions. I told them that I paid for goods and I never received them, and that the seller wouldn't answer my emails or phone calls. The $26 was back in my account the next day. You should be able to dispute the payment because you did not receive the goods that you paid for, and if you can't, then I would switch to a different bank because that is bull****.