I think 16'X 20' cage will be a great cage for 1 spec caiman. If you are keeping it indoor enclosure and 16’ X 12’ should be ok?? Someone here may disagree. At the C.S.G, I've heard some caimans, crocodiles are kept in small enclosure and they are doing fine. I’m not trying to say they should be in small enclosure, I think they should be in comfortable size cage and they can roam freely. In the future I plan to use 16’ X 30’ out door enclosure with huge pond because my plan is to house two or trio spec caimans.
My beautiful woman will say "Oh boy that she has crocodilian freak boyfriend" when she read this msg. lol