I think that by intervening with rattling cans and the like, you are adding to the stress that both cats feel. A non-intrusive method of intervention would be to start feeding the two kitties in different rooms with a closed door separating them and guaranteeing them each their own space and the chance to eat in peace. This should go far to diffuse one of the main sources of rivalry and hostility between these two.

If they are fighting over a favorite sleeping spot, I'd just let the two of them work it out. Presumably your house has multiple sleeping nooks, one of which the loser cat can adopt as his own.

Is one of these felines a new arrival at your house?

Cats typically work it out with a lot of hissing and posturing but rarely drawing blood. I'd let them alone to establish whatever they need to establish in terms of heirarchy or equality.

No they've been here since we moved in two years ago. They don't fight over food or sleeping spots, but I do think that I did fuel the fight in some way. Plus last night they weren't really rattling, Dustin clawed my thigh trying to get to Muffin. I think the fight probably wouldn't have happened if I didn't grab Muffin to help her get back on her feet. I've helped the cats before if they slip, sometimes on a window sill, just grab them around the ribcage, just under the arms, and lift them up high enough to get back on four paws. Muffin was hanging over the computer tower, her belly on the top with front legs on one side and back legs on the other and was scraping her claws on the metal case trying to pull herself up. Now this is a regular case about 2-2.5 feet high sitting on the floor, that they both sleep on regularly, I don't know why she got frightened which is why I think she was half-asleep/almost all asleep when she shifted position and started to fall off. I think she freaked and when I picked her up she had a frantic energy that set Dustin off possibly fueled by my proximity (maybe he thought she was going after me). They are running free now, this morning Dustin was whining to get into my bedroom so I let him and she came down from her cat tower and they kinda sniffed each other, walked a bit tentatively around each other and then seemed to forget everything when the dogs got up. With two teenage puppies running around the cats have other things to pay attention to, lol.

They don't wrestle often with each other but if they do and one starts to hiss or spit I'll just call out 'HEY!' and they step away from each other and then aren't interested in it anymore. Next time I'll probably let them get up by themselves but seeing them scrambling, clawing at something to pull themselves up on, if they seem to struggle a bit too long I feel bad for them and just give them a hand. I'll keep a can of coins/air around just in case.

When I was younger I once brought a cat home from the shelter and just introduced her to the resident male cat. Well she went tearing after him and luckily he didn't want to fight so when I could grab her I put her back in her crate and took her back to the shelter :( When I introduced these cats to each other in their new home I had Muffin set up in the bathroom for the first few days and would swap them out to get used to each other's scent before I let them loose together in the apartment.
Last night's fight felt like the one years ago rather then two cats finding their place. They've been together since fall of 2008 and the only issue they had was some food warning/aggression. A family friend out in the country had a litter of kittens in his garage/barn. The mother was a neighbours cat and so my friend got left responsibility for the three kittens. He never cared much for cats, actually I think he hates cats, but he wouldn't let an animal suffer so he fed them some cat food but only one bowl a day in the morning and in separate locations for the multiple animals (he had two large dogs). When she first came she was naturally possessive of her food because she was conditioned that it was only there once a day and if you don't eat it all right away someone else will. I corrected her and the hissing at the food bowl went away quite fast when she realized she was getting plenty of food. So I don't think the cats are fighting for position or such in the house.

The fight erupted with no warning signs and lingered a bit this morning. It was more like two cats who just met and decide to go at it.

Cats do fight to find their position in a hierarchy, and sometimes a violent spat can occur if they accidentally end up in each other's space, like when your cat lost its footing. I would grab a cat to prevent it from falling too, but hissy spitty snarly screaming fights are just in the nature of the beast, and it's really best not to try to play referee.

It is too bad that you returned the earlier kitty to the shelter. If left alone the 2 kitties probably would have settled their issues and coexisted. I would have felt a stronger loyalty to the cat I owned first too, but I would have given the newcomer at least 48 hours to integrate.

I think it happens to all multiple cat households at one time or another. In mine, it usually happened between a mother/daughter pair who for the most part were best friends and rarely seen apart. But when they got into it.........THEY GOT INTO IT. But one eventually ran, and it was usually the daughter. Hard to tell what set my pair off, but I'm sure it was one transgressing into personal space when the other wasn't in the mood to share it.

Yes, it is scary and I don't know what I would've done had one of them not yelled 'uncle'. Prolly let them have it with a bucket of cold water.

I was young and I got her because my mom wouldn't let me take my cat from home (even though he was obviously MY cat) so I'm older and mature enough to know I got her for the wrong reasons. I do think of her and hope she got a good home.

I'm sorry this happened to you in the past. I hope things settle down between your two kitties now, but I'm certain they will. Cats really do fight and it is a part of their normal social interaction. Try not to worry or feel compelled to control the situation. They will sort it all out and it is unlikely they will be injured in the process.