Epaulette Shark (Hemiscyllium ocellatum)is a great shark that is a smaller reef shark. it is a light brown with black spots covering the body. a 150 gallon tank is cutting it close to size. he will probably need a larger tank (200-240G)
a good rule of thumb; the tank should at least be 1.5 by 4 times the length of the shark. so if you have an 18 inch shark the tank needs to be 24 inches deep and 72 inches long which is approx. 150-200G but thats if the shark stays that small!
by the way l got this info From Bob Fenner in his Book, THE CONSCIENTIOUS MARINE AQUARIST