I believe water changes are the key in fry growout tanks.
You should be closely observing the fry, and culling out any mutations.
In any spawn, there will be a number of individuals with curved spines, or distorted gills etc, and many of these mutations aren't obvious at small sizes, one reason to hold off selling.
At very small sizes most LFSs and individuals will expect to pay significantly less than you might expect to get.
I like to take fry to my local aquarium society meeting and BAP them (donate to a breeders award program) or offer to trade them to other members for some fish I haven't tried.
If simply unloading them is your aim, take a dozen or more to your LFS and trade them in for fish food, store credit, or something you need. I find at 1" my LFSs give less than $1 each ( sometimes 2 or 3 fry per $1) depending on the species.
