No way.. The moment arapaima gets bigger than the koi, it will be a fantastic eating session.. Arapaima can eat anything that fits with their mouth, i saw a video of arapaima (39") eats an arowana around 14-18".. There's no way a koi can defend itself to a monster like arapaima..ckyap;1783602;1783602 said:Hi .. everyone .. anyone has experienced or seen arapaima mixing with koi fish ? ...... Thanks . in advance ....