I can only comment on what happens at the shop I work in.
Any fish that we take in is sold on.
Just today I persuaded an old lady(must've been at least 70) to bring in her menagerie that she had in a 20 gallon tank, (list below), as she really liked the look of dwarf honey gouramies and said that she was waiting for her current fish to die

before buying them.
I said that we would re-home them and let her take the gouramies.
1 6"elephant nose fish
2 6" koi angels
2 3"albino tiger barbs
3 pentazona barbs
2 5" silver sharks
1 6" glass catfish
2 6" golden sucking loach (cae)
Needless to say she was well overstocked
I did a good thing today (pats himself on the back)
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