Hi, I have two Pleuros. I cleared my entire stock of fish that I'd grown from tiny so I could house my Pleuros with no worries.
What size is the tank mate? I hope it's at least 2.5ft wide as Pleuros are open water torpedos, they are always swimming around and at times very fast.
You should think about getting more than one Pleuro if you decide to get one as they shoal in the wild and hunt in packs, also mixing with an Aro and a Dat could be problematic.
If you get the fish at 30cm and it's been on live feeders all it's life changing to dry or frozen foods is going to be very difficult. Mine eat anything dead but then they have never been given feeders, well they did once but decided that goldfish taste like crap hence I now have 3 large goldfish living with the Pleuros.
I'm not too sure how aggressive Pleuros are as I said earlier I cleared my Aro, Gars, knives, bichirs to get mine and all that has shared their tank were the 6 goldfish now down to 3. But these 3 have been fine for the last 4 months.
To finish, Pleuros are the best and most charasmatic fish I have ever kept and remember it's Blue for boys and Green for girls
Good luck