Eric is correct,
If you paid by gift, he has no requirement or expectation to send you anything.
You cannot file a dispute since you gave him money as a gift (gift meaning you expect nothing in return).
People have tried many times to get their money as gift back from paypal with no success. If you try cancel it through your credit card company, paypal will sometimes send it to a collection agency and you will still owe them the money, but now it will count on your credit report agaisnt your credit score. Usually not a good idea.
Many people will sell tons of fake items on multiple forums for a low price. They do it thousands of times, hoping that even once they get someone to send as gift. If you sit on a computer and do it all day, you can make good money if you dedicate the tiem and do it properly. People even sell things they know nothing about. They could have just looked up the most popular aquarium, found a picture of it, threw it on an aquarium forum and hoped for someone to pay as gift. The amount he sells it for can't be too high ($800) so that someone gets suspicious or unwilling to pay as gift, and it cant be too low ($3) so that it is not worth his time to scam someone. 80$ would fit in this category.
Right now all you can do is try get ahold of him and hope for him to send it to you, although he is not legally required to do so.
How long have you been trying to get ahold of him, I wouldnt assume he is out to scam you just yet.
Sorry.
