Okay guys, first off... I got the idea from a friend who has her own catering business. She used a bottle cap, and I STILL have it. I find, if you pass someone a card... It tends to get tossed away with the receipts and papers left in one's wallet... However, if you become more creative, it tends to stay. Or at least, get passed around to someone else.
My idea, is to place on one side the website name, and contact information (flush against side), and the other side will having something loose in there, such as a small handmade baked clay Betta, and perhaps some confetti. It'll be a trial of 12, to see how well it picks up and whether or not it would work... Shipped to them with their order, or given to them in person.