Thanks so much for the response :)
Alright 3 yellow tangs it is. Hope they get along!
As an update on this:
I got the 3 captive bred yellow tangs from Biota (via LiveAquaria). My first reaction to getting them was how *tiny* they were. Each of them about 1.5" long and super thin. Not in an unhealthy way, just the normal proportions for such a small fish. They all ate right away, and in the 2 week TTM process I had them eating frozen food, nori and then eventually rocks with some GHA from my tank that I wanted them to get a taste for. They ate all of this without issue and got along pretty nicely in the 20 gallon QT tanks.
Then after a few more days of observation I decided to put them into the DT as they seemed quite healthy. Based on this thread I was very concerned about the reaction I'd get from my Kole tang. Since I didn't actually have a perfect backup tank for my kole tang (my backup tank is only 20 gallons), I got my fish trap ready but decided to see what the kole tang's reaction would be to the tangs.
For reference here is the size differential:
Anyways, it has been a week so far and the kole tang has not taken the slightest interest in the yellow tangs. The first couple of days for the tangs were a little rough because I've got 6 damsels and 2 clownfish that have their territory and were prepared to defend it. So the yellow tangs were bouncing around from spot to spot trying to find anywhere a damsel wouldn't attack them. Fortunately the tank is 8x3' so there was still quite a bit of safe real estate.
That settled down after a few days and now the tangs are swimming past the damsel real estate without getting much of a reaction. The yellow tangs were showing no aggression towards each other in the QT process and were doing a lot of hanging out together. That has not translated to the DT. The tangs are doing a lot of jostling amongst each other and trying to figure out their hierarchy. But again the tangs are tiny and the tank is huge so they are having no issue swimming away from each other's aggression. The first few days one of them had some nipped fins (which could have been the damsels), but as of today all of them have full fins so they've healed from that.
I thought maybe they'd get a little aggression from either my lawnmower blenny or bicolor blenny, but neither of them seem to care either. So at this point things are looking pretty good. I also should note that my Kole tang spends like 30% of his time fighting his reflection in the acrylic so maybe that is a helpful factor.
Either way I'm very excited about how everything has gone thus far, and am greatly enjoying my tiny little tangs swimming around eating algae.