My red tail shark has been chasing one of my platies and it has died,
Will it now start chasing the other two platies and my four catfish.
I dont want to get rid of the shark, what can one do.

I had the same problem with mine. Despite it *supposedly* being a community fish the evil little swine constantly harassed all my other fish. I would never have a red-tailed in a tank again and also like you I didn't want to part with it. So, I pretty much avoided small, fragile fish purchases until it eventually died.

The red-tail black shark is sold small as a "community fish" but can be very territorial, especially when bigger and can be a bully too. It'll probably start on the other platies now so not much you can do if you don't wnt to part with it. Does it have a hiding place, cave or something?

Yea hides under large rock.
Is there no other species that it would not bully

Pirahna? Honestly, though, I never found one it wouldn't chase. You could try sticking to Angelfish or a good swarm of Neons (safety in numbers) so it isn't the largest thing in the tank.

My red tail shark was lovely until he grew up, then he killed and ate all my gold barbs, guppies and finished off with a snack of five neons then went on to bully my gold mollies. I only solved this when I put him in a larger tank. He is now a reformed villian who has no longer a taste for neons.

Mine has never bothered my angelfish or anything larger than himself so maybe try putting it with bigger fish as red tails only seem to bully small top swimmers.

Yeah he'd be less likely to bully fish larger than himself. As much as you like it, and they are a striking fish, I'd take it back. I had one and a flying fox and they were constantly fighting with the fox getting injured so took the shark back. Guess what? A week later the flying fox died.

At the moment, my red tail shark is getting a taste of his own medicine as my angels are protecting their new eggs and are talking it in turns to bully the shark.

Good. I have a large golden gourami, adult size and bought a small opaline one. The golden started to bully and chase it relentlessly until one day the little fella turned and retaliated. Now the golden's scared of him and he's twice as big!

I did have my shark in a 60L tank when he was as his most agressive. I invested in a 180L tank and found that he calmed right down with lots more space, he is still very territorial though. My shark is a very impressive fish but I would never have another lone one again after he dies.

You're only supposed to have one really though. Okay it's not set in stone like having just one male fighter, especially if you've a very large tank. Two or more and they just fight all the time usually with both trying to establish dominance. Look at a tank-full in the shop and most have split fins from fighting! They'd either be bullying other fish or each other. I'd never have one again. Red-finned sharks and the albino variety are better for a community tank as they're not as aggressive.

Looking in pet shop they have a tank with about six red tail and lots of barbs, they seem to get along.
Would a shoul of barbs help

Not sure but you could try. Not tiger barbs though as they're notorious fin-nippers.