While I don't know what other fish you have in the 150g tank, aPB and YT s/b able to co-exist. I've had my PB for almost 2 years and he's absolutely my favorite. When he first arrived he did contract ich. Treated him w/copper( which you can't do is you have a reef) and since then he's been fine. They can be a bit tricky during the acclimation phase but after that their pretty good and hardy assuming you provide the right water conditions, and feed it lot's of Nori. The key is to get a very healthy specimen from the start. make sure he's got very good body definition, clear eyes, no signs of wear and tear and that he is eating well. As far as the hippo, also a good fish. Somewhat more sensitive to ich and does spook easier. he will dash in and out of his favorite hiding places but most of the time would still be visable once acclimated to his new home. I also like hippo's but the PB is by far my favorite! All tangs do better in an established tank w/ L/R, L/S and good Protein skimmer. Best of luck!
