It really depends on the quality and where you try to sell them.
A LFS is generally the worst place to "sell" them as they usually will try to give you store credit and base that on what they usually pay for those at a wholesaler. Store credit would only be fair if the basis was the stores sales price, otherwise it's a ripoff.
If you breed fish at a consistent rate and have good quality, I would try to sell them to a local wholesaler. You may not make the most money, but you usually can unload a lot of fish at once.
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