Just my 2 cents.
I have 3 tangs. Sailfin, Yellow, & Hippo all together.
When considering a new one-
Make sure eating and very healthy before purchase.
Tang care basics: feed well.
Plenty of nori-algae strips.
Excellent mix of various frozen.
Having them together:
Try to add all at the same time. If not, still possible-
Add at night after lights out and settling down of other established fish.
Gives new comer time to acclimate without being pestered as much.
Change a couple rocks around here and there(only if you have to) to throw off initial aggressions. (note: I added all 3 of mine at different times(not together) and all with success)
Last- Hippo tang IS a big time "waste" maker.
Still, this can be dealt with and still be successful.
Plenty of skimming!!!! Keep up on ALL the parameter levels from depletion-
and do Water changes MORE often.
SPS can be kept with this guy(hippo) but the fish makes it more challenging.
If you don't mind a little more work- then you can do it.
Also, make sure any thing(corals you have, frags etc.) are "nailed" down. Aqua puddy, glued "secure". Mr. or Mrs. Hippo is super clumsy. Can knock things over all the time. Even when given adequate space. DO leave room for adequate swimming space!
(reefs are easier to keep with less fish) But don't let that stop you. It's about what you want and what's your commitment level. You have to decide that. But stick to it! 'An ENJOY!!!