Hello all. I have two fish in my 2og long display, a pair of tank-bred true percs from ORA. For some back story, I have had these fish for almost 2 years. I ordered them at the same time and they've been together ever since, and there have never been any other fish in the tank. While they're both very similar in size (perhaps just over 2"), there has never been any aggression whatsoever. They've been inseparable for the last two years. Neither one seemed to make a play for dominance at any point. Now, however, things have changed. The one clown, which has more black coloration and may be a bit bigger, is bullying the other. The one who is being bullied keeps running away and submitting (doing the "don't hurt me" shiver), but the aggressor keeps piling on. Every time one of the torn fins heals, another appears a few days later. They can be seen together during the day, but at night they sleep in separate corners of the tank. They've always stayed together at night up until this point. The aggression has been going on for a week or two. No changes at all have been made to the tank. I have a bit of nuisance algae, but that has been there the entire time I've had the clowns. If anything, the chemistry has never been more stable.. the few SPS frags I have are showing great and recent growth. Is the slightly larger clown finally deciding to establish dominance and become the alpha female? It seems odd that these two would get along so peacefully for almost two straight years, and then start fighting. When should I consider separating them? I am worried about the clown being bullied. I have other tanks and space for the bullied clown, so it wouldn't be difficult to move it. I don't want to interrupt a natural social behavior to establish dominance, but I would also hate to see the poor thing die because of my inaction. I also don't want to keep them separated. I'd much rather them be together. Any help would be appreciated. Thank you very much.