Newbie Questions - feeding young silver arowana.

[enghai]

Hi,

Just started my very first aro.
Bought a 3-inch silver for my 3-ft bare tank running OHF.

Previous experience only with gold-fishes and guppies.
Ran the empty tank for more than a week before I bought this fella home.

First two days, it hides under the OHF away from the detachable LED lights.

Managed to feed it with pellets at Day 3.

Question 01
Not sure if it is normal that my silver is always on the water top, does not swim either to the middle or bottom of the tank.
Do I have to switch to sinkable pellet to lure it down?

Question 02
I have mixed pellets and dried shrimps + dried mealworms for the aro.
At 3.5 inch now, do I need to change to MP or live mealworms?

Thanks.