I guess you know your own fish best and you say he's very aggressive...
couldn't predict what is gonna happen, but there may be trouble ahead.
Better wait for the experts, i never had any jewels.
If you decide to put him in, take time to observe their behaviour and be ready to take action if nescsary.
I trained my Aggressive Vieja by threatening to net him once, after he made my O knock himself out, and nobody messes mith my O! :angry:
After that if he bugs my o ,I take the net and just show it to him, and he will bounce back and stop misbehaving.
Of topic, can I see a picture of you with your cello, please???
If you post it, i'll show you mine.