I have a 30 cm Arowana right now, and I feed it goldfish and earthworms. It helps in enhancing the color, but before feeding the worms be sure to wash them.
Silver Arowanas are a good addition to a tank only if you can afford it and if your tank is large enough. The price tag is relatively small for such a beautiful fish. I have has some pretty fish but nothing beats an Arowana ruling the top of the tank and a Stingray ruling the bottom it is truly beautiful. However, it can be very hard to raise one. If you have juvenile, I suggest that you feed him krill so he gets hooked on it and when you canīt make it to the store to get Goldfish or Crickets. It can be very expensive to keep up a Silver, especially when they get big.
I have a Silver Arrowana that is 98 cm long. I bought it as a fry and have been raising it for 3 years. The most important thing I can share is that you shouldn't overfeed your young Arrowana. If your fish is fed too much too often it may develop "drop-eye". This is a condition where the eye is forced down by the development of fat deposits building up behind it. To combat this I feed my fish foods that are lower in fat. These include worms, mice, frogs, and sparrows or other small birds. You may want to exercise caution when feeding mice, as fur is more difficult to digest. Over feeding with mice will lead to tank fouling. Feathers, on the other hand, are a modified scale and are digested in any volume.
These are, in my opinion, the best freshwater fish you can buy. They are incredible swimmers, as anyone who looks at my one says. They move like a snake under water. They are also a great fish to show off at feeding time, as they will attack anything they think has the slightest chance of fitting in their mouth with lighting pace. But they also grow very big, very quickly. After 9 months I am now having to purchase another tank, so start out BIG if you're thinking of getting one.
I also have 2 Arowanas. This is my third time to venture in this hobby. I had a bad experience with my two other arowanas. When there is electrical failure, I need to use my battery oxygen just to have a continuous supply of air. My advise is not to have so many fishes in your aquarium. This was my problem way back. I had 7 different types of fish in my 380 liter tank and this was the reason why my 2 other arowanas died.
I feed my Silver Arrowana mostly frozen shrimps (sometimes with the shell) and colour enhancing pellets. The fish now has very good colour all over. It's not just silver but has red/green edged scales and strong red in the fins too, and a high gloss shine over the body. Arrowanas with a poor diet have less colour, and the top of the fish shows little or no silver scales. This is noticable on older Arrowanas, and if happens you should change the fish's diet.