Here's a little diff idea...
I do not keep p's, but I have a fish that seems to be an option that has worked for over 2 years in my predator tank with zero issues.
I have a really aggressive 18" Mono P. Bass, 2ft Silver Aro, two 12" Tiger Oscars, a really super pissed of RB Pacu, a 12" Spotted Shovelnose and a Large Red Tail Cat. Obviously all fish that love to eat other fish. In fact my Redtail cat, when he was only 11", ate my 10" Senegal Bichir.
The thing I'm getting at is, I have a 24" Gymnothorax Tile. He has always been smaller than his more aggressive tankmates, but has never been nipped, bit, or eaten. I think I have figured out why.
Fish don't eat him or look at him as a food source, because they have toxic mucous and slime coat. It's more poisonous than venomous, I guess.
Give them a try, just slowly acclimate your p's to about 1.008SG, and add him/her at night.
Truly awesome fish in their own right.
Check mine out on YouTube. "smnkm4ehfer"