The best place to take unwanted fish is your local Mom & Pop stores.

Every time we walked by that store, it broke our hearts to see that huge fish in that tiny tank. Fish and reptiles should live in their natural habitats and are not appropriate pets. Even veterinarians do not know how to take care of them. We hope all the captive fish and reptiles find decent homes, but we won't miss that awful store.

Pet stores sell betta fish to people who don't know how to take care of them and ..

Once we find this out we need to take the fish back to the store where we bought it either that day or as soon as we can. But when you keep that fish knowen it's going to out grow the tank and be unhealthy til it's to big or to late for the store to take this fish back. Then it's no longer a mistake, it's animal crowdie. Then when you do take it back to the fish if they do take the fish. Like the petsmart here the manager of the fish department will either call me or try to find a responsible person to take it.

What do pet stores do with all the unwanted fish

I doubt pet stores will take in rehoming/surrenders fish but you can always try Freshwater fish such as goldfish, betas, tetras, etc are pretty easy to clean up after and take care of. Betas can live in a fish bowl but most other kinds do better in a tank set up with a filter and air pump, which is a little more work. Pretty much all pet stores have freshwater fish and from what I've seen, most stores take pretty good care of them.

Most LFS / LPS won't even take donations much less trade/buy

Yeah at my store we take in adoption fish but it is usually limited to livebearers. I have adopted fish from stores as well. I really like the "adoption first" Right now I have a snake, box turtle, bird, hamster and fish that I've adopted all from Petco.

There is no room at Pet's Mart for adoptions .