No one really knows for sure how it's caused, just theories. I can reassure you though that kril is very low in fat. There are also suposed home remedies for curing it such as putting your tank on the floor forcing your aro to stare up more often, floating a ping pong fall, putting your fish in a decent sized pond or corrective surgery. Though surgery is the only shure fire remedy, but like you probably know an arowana can live a healthy long life in aquaria with de.