You won't need a liceanse, since you are only doing it on a hobby scale. However you should be aware that many fish sites consider one of the distinctions between a hobbiest and a commercial seller to be a website which advertises their product.
In my personal experience, you are not really likely to have enough offspring to justify having a website. You would be far better off to simply meet the posting requirements of fish forums and advertise your offspring for sale in the classified section.
One of the questions you are going to be asked with that many pairs is can you guarantee that the offspring are purebreds rather than hybrids?
Just some food for thought.