the tank is 55 gallons, and it has filter, etc. will they get along?, i was gonna put a green terror with my african ghost knife fish, and people told me yes, go ahead, but then i also had read that some greeen terrors are so violent, they attack humans, and ignore the tinfoil barbs, so i got the idea of the jack dempsey, but i dont know, should i mix my african ghost fish with this jack dempsey fish??