Chapter Text
Tony was drifting along, nowhere in particular, when he detected a minute change in the water. His elegantly languid dorsal fin snapped to a more rigid stance (the equivalent of a scowl in a betta splendens).
"Dammit, if that stupid human in charge of my living arrangements has let the filter get dirty again..." he complained as he swam over to the water recycling unit in one corner. A quick inspection showed no problems there, and he was just about to return to his favorite thinking spot when he caught a glimpse of color out of the corner of his eye.
Every nerve jumped to high alert as he barrelled over to an unknown betta - ha, the source of the water change, for sure! - and began headbutting him.
"My tank. My tank. Tony's. Get out, you piscine bundle of muscles..." Tony's voice died off as he got a better look at the newcomer. That was one big betta, at least half again Tony's weight, and in absolutely perfect condition.
But his tail's not as red, Tony thought. Definitely not as red. Probably not. Maybe not.
He carefully avoided checking his own tail, just in case.
"Hi, I'm Cap," the new fish said, extending a perfect fin.
"No, no, noooo, you can't be here, go away, mine, mine," Tony chanted, while frantically trying to get between Cap and the north side of the tank. That side.
"Hey, no need to fuss. I wasn't going to fight you," Cap protested, all gleamy scales and amiability. Which didn't make Tony feel any better. No pun intended.
"Go away. Don't be here."
"Why not? Oh -" Cap's eyes widened and his mouth gaped open. "That is one classy lady!"
Tony resolutely didn't look at the other tank, not seeing the swirl of orange and gold there. "No! Bad Cap! Mine!" he shouted, and headbutted the oblivious newcomer again.
"I'm sorry," Cap said, tearing his eyes away from the other tank. "I didn't know she was your girl."
"Why do you think I keep saying 'mine'?" Tony asked, exasperated. "You think I'm trying to claim the gravel in here or something?"
"Hey, it's okay. Can't we just be friends? I haven't had a friend for ages," Cap said wistfully. "Besides..."
"Besides what?" Tony asked with suspicion.
"If we keep fighting, the human will have to take me out of this tank. And since there's only one other tank in here, I guess I'd have to go in that one."
Tony stopped dead in the middle of another charge - no mean achievement for a fish - and gave the situation some thought. Which was hard with another male betta over here and Pepper over there, but he managed.
"How do you feel about a temporary cessation of hostilities?" Tony asked, swallowing a few gulps of water to try and make himself look larger. "Since, after all, if we keep fighting I would totally plaster you all over the glass."
"Sure, Tony, I'd like that," Cap said, earnestly.
Tony flipped his tail jauntily in response, definitely not looking over his shoulder to see if his defeat of the bigger fish had impressed Pepper. One could always hope.