I JUST successfully added an adult sohal to my 6x3 260g. That tank has the meanest SOB Achilles ever. The tank is pretty open but there are lots of hiding spots.
I tried the following on that tank...
1. Introduce scopas tang at night after a HEAVY feeding during the day.
Result = scopas was torn to pieces but alive. Scooped him out with my hand.
2. Adult powder blue added at night. Seemed like things were going ok although he was hiding.
Result= Dead when I got home from work.
3. Majestic angel.. 12 days in acclamation box. Its an angel.. achilies ignored him in the box..
Result = Achilles went ape shiet, slashed him up, hiding in top corner, Achilles going after him.
At this point it was a battle between me and the achilies... That angel was going in the tank!!!
4. Last ditch. Qt'd adult sohal. Added about 40 lbs of live rock to the DT on Sunday. I blocked many of the popular swimming routes and hiding holes. Monday, huge feeding, dumped the angel, the scopas, and the adult sohal in there.
The Achilles was overwhelmed. He was trying to pick a fight with the new fish but he would chase one.. then see another one and chase him. He lashed out at the sohal twice and the sohal made it clear that he was not to be messed with. Achilles suffered a small fin tear.
Tuesday.. fish look pretty chill. Sohal happy as a clam swimming around. I pulled the extra live rock out this evening. The scopas is still kind of hidey... but, well, scopas.
The other tangs in the tank are a blonde naso, Desjardini, and hippo. I thought I could keep all this until fully grown in the 6x3 but I do think a bigger tank is going to be neccessary.
So, that is the long story on my tang battle.