I may need to go with a Koi kind to get the reddish
The 20g and 30g I have are both community tanks, have two angels in both (total of 4) and so far they seem to be nice to each other and play well with the other fish. From what I have gathered it is as much the personality of the individual fish as it is their species.
With the 3 you might have a bonded pair and the other fish is jealous or the male is showing his machismo towards another male.