sadly, there is people out there who expect the local pet store/fish store to know everything about everything, which is literally impossible.
the first few fish i bought were just "looks nice, ill have it."
then i bought a victorian cichlid by mistake, astatotilapia latifasciata.
the male was a complete jerk and about a week later i returned him and got another male (but kept the original female i had)
he grew, gained colour, bred with the female (i now have 8 fry) and within a few days i seen him being a jerk to others including:
-dragging my pleco across the tank by its fin.
-pleco has a bit missing from his tail, and one of the fins behind the gill (pectoral fin ??)
-a small silver shark with the tip of its dorsal fin missing.
-one of my bigger sharks (approx 10cm/4") missing the lower tip of its tail.
-my other male cichlids spin around quick and flare up if he ever approaches from behind.
the breeding pair went back to the fish store pretty quick, and i still have 8 "jerks" to return when they grow up.
caveat emptor
i now note the fish species and go home and research it before purchasing.
if i want it i come back to the fish store a 2nd time. its a pain in the arse, but it beats coming back to the store a 2nd time to return unwanted fish.
for some reason, returning fish to the store makes me feel so guilty... like im returning an unwanted dog to the pound or something