How big can you grow a fish in a 6ft tank?
 

As stated in the title..how big can a fish grow from say a 1-2" juvenile?

I bought a 1 1/2" Vlamingii Tang a year ago and it has grown to about 5" in length. What can I expect in a 6ft tank?

depends on feeding, water quality, how much free swimming space for exercise, etc. You'll likely see a lot more growth if all these things are good.

Thanks..I guess what I'm looking for is maximum potential if all of the things you stated are met.

For instance..say a Sohal tang..max out at 10", 11" etc?

Well, a Vlamingii Tang can hit 24" in the wild, so I would say minimum 12" in captivity, all conditions being met. Now, can you maintain proper feeding and proper water quality? That's a tough one. If he's grown to 5 inches in a year, iI would guess you might see 10" eventually. Typical aquarium care, you might see 8". Unfortunately not a lot of people have these, so it's hard to get "from experience" feedback.

I guess where I'm going with this question is..if there is potential to grow out a fish I would rather buy smaller juvinile and raise it to show size instead of buying a much larger adult specimen (7-8"). Eventually I would like one really big fish in my future 240g (healthy and happy of course).

Oh, well why didn't you say so. I have seen a naso grown from a juvenile to really fat 11" adult. I've also seen Sohals grow quite a bit too, so yes, there certainly is potential to grow a large fish from a juvy. Which is the way I'd go if it were me.