Width 2ft is enough to house an Asian aro be it a Red or Gold.
What is more impt is the length and not the width in order to really enjoy the aro.
Aro in tank environment generally do not grow that big, probably around 24inches +/- , unless its a pond.
Also, feeding to that size play a part in the growth too.
Asian Aro has the highest growth rate in its first year of life and will gradually slow down as it ages.