My 90 is under construction but will include 3 tangs, all introduced at the same time. I will have a purple and yellow for sure. The other tang will be either a powder blue or a blue hippo. My heart wants a powder blue, but my brain is torn on which one it wants. On one hand, I would think a powder blue would make sense because the tank fits its needs better than it would a blue hippo. On the other hand, blue hippos are much more peaceful community fish than powder blues which can be quite aggressive. What will likely happen is that I will try out a powder blue then replace him with a blue hippo if aggression becomes an issue. If I have to do this, I will remove all tangs, QT them together, then reintroduce them to the tank simultaneously.
Other than that, I will probably have a pair of clowns, a flame and/or coral beauty angel, and various smaller fish including wrasse, blennies, gobies, etc. I will base my decisions on the smaller fish on the available space in the aquarium. I am planning on doing fairly minimal aquascaping so as to create ample swimming room, but not so minimal as to eliminate shelter. Corals will likely be mostly SPS.
I am going to be running the tank on a 30 gallon sump/ with refugium. I may add a second small aquarium to this setup for additional rock. My skimmer is a Vertex IN-180, and I have an OTP return pump. My lighting is a 6 blub T-5 fixture and I have a 48" LED strip (all blue) for supplemental lighting. I will be using BRS Pukani and Reef Saver rock which I am currently curing in rubbermaid containers with lanthanum chloride to remove phosphates. But as for now, the tank is not up yet. I have everything I need except I have not yet sectioned off my sump or stained my DIY stand. So once those things are done, I'm in business.
So that said, this is going to be the first "large" reef I have had. I've had a 30 gallon reef and an 80 gallon FOWLR in the past, but I am a big-time student of the game. I take every chance I have to ask other reefers about their personal experiences, and also consider available general information as well believe it or not. So essentially, I have all of the theory nailed down and now I'm getting ready to apply it. I really can't wait. I haven't had a tank since I got married a couple of years ago and man do I miss the hobby. I am a reef nerd for life, I'm afraid.