[ZivaD]

What is the current size of your redtail? He may be behaving himself now, but that doesn't mean he won't change as he matures/grows - especially since you have already seen aggression towards the one molly. Unless you have had him prior to getting this new tank you have only had him for three weeks at the longest, and seen aggression in just that short time. Being cool looking is not a good enough reason to keep incompatible fish, jmo.