You fail to tell what type arowana you have. With both of my silvers and my black I have found that changes in there environment(including medications) can send them into a food strike. Many people have had their arowana go through this and it can last four a while( up to a month is not uncommon).
I have found with my three aros the best way to get them out of a eating strike is to offer little or no food. I would only offer food once every three days and for only a short time, remove the food if not taken within a minute or two.
This advice given is blind, it would be better if you provided more info such as arowana type, size, diet, tank size, tank mates. Also what is the general health of your tank, no mention of water params. Do you no about the nitrogen cycle? What are you ammonia, nitrite, nitrate and pH levels. How frequently do you change your water?
This may seem like a lot of info to give, but it is helpful when trying to figure out what is wrong.