If it is wyckii it is one of the more aggresive fish for the aquarium.It should be housed alone as it will kill any other tank occupant.Usually sedentary until night time or food time.
Anyone that keeps a rtc will know that although they would outweigh and outmouth a wyckii unless the rtc could clamp onto the fish the wyckii would not only elude the redtail but take him apart bit by bit.RTCs reputation is by size and like any bully often cannot take being bullied themselves.