i knew they were hardy, but a lot of animals seem to be hardy when conditions are ideal only. apperently not these ones. i don't think it's turning black because of mating, but not sure. has he ever done that before? i think you would have seen it if it was because of mating. what kindor set up do you have? and does it seem healthy other than that? i've seen ones that were blaskish/brownish and they didn't look healthy, but i don't think thats the same case with you, esp. cause you've had it for 6 years. thats weird though.