yes, that's right.
I brought my 6" aro silver on Dec 31, 2005 and by end January 2006, it grows to 8" and I only feed with pellets and dry freezed shrimp.
He now house in 4ft tank and probably need to upgrade to 7ft soon.
So, this is better to start with a big tank possible. My 2 cents comment.
Hi i thought my tank (60g) would house my 6 inch silver for a while, well think again i got him in november 05 and now febuary 06 he is now 8-9 inches and is getting cramped in my 60g as he is trying to jump out, so i got him a 115g (20inches wide) last weekend. and he is having a ball. so if your gonna get a small one3 inches or more is better atleast get him/her a 100g until it needs to be moved.
To house monsters you need a monster...that may be true...but i see like 50 people on this site with a 120 gallon tank that has 20 arowannas in it...so really i think one will be fine in a smaller tank untill around 10 inchs