I don't think he is saying only 1 Oscar for 150G. He's saying don't settle for minimum.
I agree that a 150G+ is best for these fish...whether you keep 1 Oscar and/or a couple of other fish or a group of Oscars. 75G is the min that any Oscar should be kept in but 150G or bigger is ideal.
These fish need room and the larger the tank, the more stable their water will be. (as long as the filtration and maintenance requirements are met.)
