My fish all seem to be the happiest when I take them out of the tank and put them on top of a table, they start to jump and wanting to play.
Just kidding ?
I don't know that fish are friendly towards people, I can tell you that some are very naturally "shy" but most likely from stress.
Others just want to eat all of the time so they'll hang out right in front of the tank and follow you around, cichlids are known for this, my angels, discus and African cichlids all behave this way. If this is them showing friendliness, so be it, I think they are just begging for food.
I'm sorry to sound so negative, I just don't think fish have emotions as humans do.
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