I had this problem with my RTGG eating everything, even my tinfoils didn't get a look in and they're quick as hell. I used the above mentioned tube method but this just seemed to help my bottom feeders. The solution was easy in the end. My RTGG goes to one end of the tank at feeding time and i'll drop in a steady flow of peas, pellets, prawn, allsorts of stuff. Whilst she's preoccupied with stuffing herself at one end, i drop food in the other end of the tank for the other fish. It works brilliantly. Word of warning though, if you don't keep a steady flow of goodies preoccupying your arowana it will undoubtedly notice the feeding activity at the other end of the tank and it will go and upset the other fishes mealtime by eating their food and you'll be back to square one. Good luck.