4 and 5 foot tank tangs

[korkus]

I am basing this post on the Reef central tang tank size post found here:
http://www.reefcentral.com/forums/showthread.php?t=1946079

With 4 and 5 foot tanks (75 gallon +) you can house Ctenochaetus tangs and some mimic tangs are recommended. My question is more an understanding on why a 120 gallon tank is not recommended for 2 of these tangs. I have always heard that if they are of different shape that they wouldn't fight as much.

So theoretically you have 120 gallon 4' tank with 120 lbs of rocks with the upper half high enough for swimming. You were to supplement with nori. You add a juvi tomini and a juvi chocolate tang at the same time.

What is the concern? Is it they may fight? Is it territory or is it cramping them in 4'? If those are true why can one spot foxfaces coexist with out issue with both in a smaller tank?

The nori should help with them grazing too much. I don't want food to really be the issue. I am really just wanted to learn about why tangs have a problem being together even in different families. I understand 4' is not optimal but if you are recommending them for 4' I don't think the 4' issue applies for 2.

I really am interested in what people who have kept multiple tangs and know their behavior have to say.

 

[Shellyfish]

I have a mimic tang and a yellow tang together, they've been together for 2 years now and their is the occasional showing off to one another but no major issues. I tried to add a Kole tang and the yellow bullied it to death. I have since added a hippo tang, and the three of them all get along fine. Mine are in a 5 foot tank. I think personality has a big part in how they get along. My mimic is really mellow, but doesn't put up with anything from the yellow.