My two Onyx were babies when I purchased them and put the in a NC with a BTA, so not sure about loosing black color. They are now almost 2 years old a maybe 75% black, 25% orange and of course the three white bars. The bigger of the two is more black than the smaller one. The spend most of there time in or around the BTA. And like ian20 says they are aggressive and food time, there teeth kind scatch me when I am feeding the corals. Little nippy. I like have the BTA in the tank with them and so do the clowns.