well the most common way is to find a store that has a GROUP of VERY young maroons. in this group you should select the SMALLEST healthiest fish. once home get a clear plastic container with many holes to put the new fish in, once acclimated. the large female will ram the container for a few hours, more than likely. once her agression stops or slows dramatically you can release the young maroon. keep a very close eye on them, she will be down right brutal to him. it has been said that maroons will only back down in the threat of death, so don't be suprised if the little guy is on his last leg before the end of this. if things get too out of hand, put him back in the container for a few days. try again later. if after a few attempts have failed a new juvi is needed. sometimes they just aren't compatible. good luck
