I am in the middle of a mandarin marital dispute right now. A little over a year ago I introduced a small female to my large established male in a 225gal display. They paired immediately and would often do their spawning dance in the evenings. Everything was great until this week when I noticed the male hanging out in the corners of the tank with one of his pelvic fins looking damaged. As this was not normal I did all of the usual things like a water change, fresh carbon and gfo, and skimmer cleaning to ensure that the tank was running in top shape. However, upon further observation I discovered that the female was bullying him and would not allow him to hide out and forage within the live rock and coral. So I've moved him to my 120gal frag tank/sump which is also equipped with sand and live rock. There is only one other fish down there with him, a longnose hawk, so he should be fine staying there indefinitely. However I'll consider reintroducing him in the display in one months time or longer if/when his fin heals back to normal.
I suspect that my recent tinkering with the tank over the past 2 weeks which involved syphoning out the old sand bed to replace it with a new one may have had something to do with this. The old sand bed was 1-2" deep and consisted of a combination of crushed coral and sugar sand. It was old, cluttered and grimy but also teaming with life. The new bed is sterile caribsea select (grain size is smaller than crushed coral but larger than sugar). I switched to it for aesthetics. This was a bit disruptive and may have induced the problem. Or maybe the power balanced just reached a tipping point with the female steadily growing in size.
