Apparently my big male longear can tell it's breeding season. That, or our week of thunderstorms has him on edge. Whatever the cause, he's built a nest (which I don't mind) and is now fiercely defending it. He ignores the resident warmouth, but the other five longears (all at least an inch shorter than him) aren't able to go into that half of the tank, and sometimes he randomly shoots over to scatter them.
Now, I've seen longear nests in the wild. There's chasing going on around them, and the chase-ees often come back, probably because the nest is in a good spot. So obviously longears are fine with a little bit of chasing.
However, this is rather a lot of chasing. I've put a bunch of new sticks in to break up lines of sight a bit more and give the little guys more cover. The thing is, I can't tell if I need to do more. The small ones have apparently all hit puberty, because they're also chasing each other quite a bit. Occasionally one has horizontal bars on him, but it usually fades once the big male stops pestering them.
How can I tell if my longears are too stressed out by the chasing? They don't really act like any other fish I've kept before, so I'm not certain what the signs of stress are. They skulk around in the corners half the time, but so do wild sunfish. They aren't brightly colored, but they all have fairly bright green face-lines, so I'm not sure if they're just showing submission. Fins are perked, appetites are very healthy, behavior seems fairly normal. Is there any definitive sunfish signal for "I am stressed by this thing attacking me"?
None of them are injured, if that's important. Two have small marks that look like scrapes, but I think it's from running into twigs or such, and it could very well have been while lunging for food. The male isn't hurting them or even making contact, he's not trying to bite, he just runs at them and chases them away.
Oddly, none of them are after the warmouth. I think it's because he's too large to be food, too small to be a predator, and the wrong shape/color to be a territorial rival. They don't seem to care about the fact that he exists.