My two biggest clown loaches (one is about 1.5-2 inches long, the other is slightly smaller) have started behavior that looks like fighting. They kind of headbutt each other for a little bit, then they take a break and go at it again. They both gray out while they're doing this, but when they separate their coloring comes back. I tried to look for those undereye barbs, but they didn't seem to be out either. I just noticed this yesterday. I have just added fish to the tank, so maybe they're trying to get a hierarchy going?