The Jardini no, it will eventually kill the pbass and your other stock, I know from experience of owning 2. The knife should be fine as long as it's bigger and I'm not sure of what a clown cat is???
I would say no with the Jar. I had one, it was tank mates with pbass, until he killed them. He also killed a scomb payara which was bigger than him. They're aggressive fish.