I just go in to my LFS and speak to the manager. They'll only give you store credit.
I use to do this with my the Petland Discount but I was told that home office management frowns upon the practice. So if I'm lucky it's a private agreement. Went to see them a couple of days ago and some of the staff have changed, place doesn't look so nice anymore so I wouldn't be trading any of my fish with them soon.
Every location is different. Don't know of anyone who has an open policy about buying fish from non commercial breeders.
Also depends on what you have to offer.
Eheim #293 ~ 2 x 2217 ~ 1 X 2215***Filstar #138 ~ XP 1 x 2