It really all depends again on what type of corals you intend to keep.
Zoos, Mushies, the small type of bubble coral.. might be able to SURVIVE in T5 NO.
However, with T5 NO, you will not be able to keep these listed corals healthy and opened to their full potential - big bubble, goniopora, true octo, hammer, elegance, cynarina.. etc.
Then again.. Most of the listed corals above are seldom kept in a 2x1x1.5ft tank.. Most reefers who keep these corals usually have 3ft or 4ft tank..