k first of all its normal for arowanas to be timid for the first week, especially jardinis.
n chances r they'll stay timid becuz thats the way jardinis are.
if you really want ur jar to grow fast n bulky, then feed mealworms or market prawn/shrimp. freeze dried krill is not advised... itll cause protruding anus in the near future. and mealworm is kind of a ***** too cuz they dont digest the hard shell and itll be all over ur tank. market prawns n bullfrogs n centipedes r the best things to feed. crickets r alright.. but u gotta remove the legs and the hard shelling or itll cause a mess.
n jardinis accept pellets easily, just put in 1 in the morning, if he doesnt bite, then take it out. do the same at night. eventually he'll take it, trust me.
so ermm... good luck with ur fish. later.