how...............?

[Outdoor101]

does anyone know how big arrowanas can get?????

[goleafs]

Very very big like 4 feet possibly longer.

[NickFish]

Depends on a lot of things.
In a small tank they can grow a foot or 2 smaller than usual, but will have a much shorter lifespan. Diet can greatly affect size also.

But in general-

Silver arowanas- 4'
All others, ie) jardinis, asians, blacks- 3'

Thats in a proper sized tank.