I kept a male and female P. Retic in my 40 gallon standard breeder for 5 months after having them in a 33 gallon for 1 year.
They didn't seem comfortable in the 40 due to its dimensions.
I moved them up to an 80 gallon. Then traded them to someone with a 210.
My honest opinion, if adequately filtered and you had no other options available right now: 12-16 months tops. He will grow and need room, no way to avoid that issue.
Respectfully,
FireMedic.