I deal with my local family run pet store. He gives me store credit, which in the end is great because that way I do not have to spend money on supplies... It's basically a trade. This includes live foods, frozen foods, conditioners, decor and plants, live plants, etc. If you ar wanting to sell them just for the money... Good luck. Settle for credit, if you tend to shop there often.
Remember most chain stores get their fish dirt cheap in bulk. They more than likely will not buy.
Another thing to remember, is know what the potential buyers want; stores and individual people in your area. Will you ship? Will you drop off? Pick up only? A solid plan ensures you will not be stuck will 5-200 betta fry for months on end. Advertising is also great in our age of technology... Kijiji (canada) or craigslist (usa and canada), along with the good old methods of brochures, flyers, or word-of-mouth. Get it known what your plan is - make sure you know that you have people interested.
And research, research, research! Nothing beats hands-on experience, but having that experience backed with rsearch plus help from us... We'll make sure your hobby experience is at it's best.