I beleive 3 tangs in a 150g is fine if its 6 ft. long and you give them holes and caves in you rock to hide and sleep. I would reconsider the naso for something else cause they do like to get up and fly, a very active fish. Maybe a purple or a kole. If you stay with the tangs that dont get to large you could even have more than 3. Just try to put them in at the same time because if you let 1 or 2 get established, then they want like any other tangs coming in and thats when there are problems. :happy: