No arowana is suitable for the beginning fish keeper. The 4 foot tank you have will only last about a year, that's even starting with a baby silver aro.
I like how people are suggesting a silver, because they are cheap. Why would you buy as fish expecting to fail

First gain the knowledge and no that you can properly house the fish before you buy the arowana. There are many other fish to keep and gain experience with, which are not as demanding as arowana.