i do weekley 50% changes on my tanks anyway but i would say to do 1 more change a week until its sorted of about 25%. as long as there isnt any more aggression then it will heal in no time
I have just got a pair of HRP's and the tails have been nipped, not sure what by, possibly some blood red jewel cichlids. They are in a tank with a few community fish for the time being until the community fish are sold on.