In which case, the fish will get to be around 45cm long (18 inches approx). You'll need a bigger tank for one, nevermind two.
Sorry! It is suggested that they have around 100gallons (450L) to themselves.
If there is any way you could give him away to your local LFS and get something like a bristlenose pleco or perhaps a slightly bigger Gold Nugget Pleco. They are slow growers but eventually the Sailfin will be way too big for a 200L tank I'm afraid
If kept alone, you're more than welcome to keep a school of 6 or 7 Cory catfish (for example) in with them since Pleco's only get aggressive to their own species in a 200L tank (and you'll still have the option of some surface feeders).
EDIT: Again, I would like another member to clarify this info since I might be mis-informed.
Best of luck whatever happens!