I just met Candice and HookedonBettas today in real life. They are nice people. This guy should be ashamed. Anyways we didn't get to discuss the situation much today but they told me to check out the thread.
First thing I would do is ask this dude for a full refund or tell him you will be contacting the attorney general of the state he resides in. Perhaps even in file a report to the AG in Washington so he might be wanted in 2 states. Second if he used the US postal service this now becomes a federal offense. If you use the US post office to commit fraud, shipping the fake Bettas should count, then there could be federal charges brought up as well on this guy.
Finally, since it happened on an Internet auction site there are new laws and a task force that protect buyers. Read this article
Going, Going, Gone... Law Enforcement Efforts to Combat Internet Auction Fraud
Nothing like explaining to people in your cell block that your in jail because you suckered people over fish.
I recommend that if you are going to buy things over the internet use an AMEX card, if you have no choice but to use Paypal use AMEX to make the payment via Paypal. AMEX will recover your money and you won't have to deal with the BS from paypa whenl trying to get your money back.
I'm pretty sure you got his real name and stuff because you had to send the money via western union. Sending a warning and begin taking the necessary steps if he does not comply with your request for refund. Good luck