ok so i wasnt happy with one of my petstores method of housing their bettas they had them in these:

these hold MAYBE half a liter (erm 0.13 ish gal)
they told me they change water once a week..
TODAY i went in and they were in TINY DAMN CUPS less then 200 ml (0.05 gal)the cups look a LITTLE LIKE THIS:

But not as tall. and lids.
the fish are only maybe 4 months old and they can BARELY turn around
i told the lady who showed me (ive been bugging her for new shipments of lady cts)
i almost snapped at her. i was all over the whole
THIS IS TOO SMALL WHY?
(her answer) they stressed each other out in the bigger cntainers
me: THEY CANT NOW CAUSE THEY CANT EVEN TURN AROUND!
she was like "oh in the wild they live in smaller water"
me: "WILD YES PET NO they need MORE ROOM!"
oh i almost got asked to leave O.O