I had a PBT when I had my 100 up and running and it didn't seem like it was quite enough for it. He grew to be really big and looked cramped. I'd say 120 min.. That's just me though. It all comes down to preference. You will not find one person on this forum tell you to go ahead and get him, that doesn't mean he wont live and grow. There are people that keep PBTs in 40 breeders, should it be done probably not. It's all opinion based on how you feel about fishkeeping to begin with.
I'm about to get yelled at for saying that now. :blown: