If your parameters are stable, you can add the tang now if you want. Bristletooths aren't as bad as some other tangs as far as aggression. Just be prepared to put him in time out (in the sump) if he gets too bossy with a future addition.Sorry It's just because they have this beautiful bristletooth tang I was planning to get and I know they need to be added last so kind of wanted to rush the stocking to get it. Probably not a good idea. Will try to slow down. I can't add the tang sooner right? Also I am planning to add corals sooner or later. Mainly be lps dominated.
(By the way, This is what I was talking about before. You can't plan everything. If you're in love with this fish and you can provide extra algae for it, then go for it)