I just bought 2 tinfoil bard fish and i would like to put together with my yellow tail arowana but my arowana just 4'' and that tinfoil bard fish is bigger than my arowana...
i would raise the aro by itself for a while till it gets to about 10".
regarding your other thread: was the aro doing OK before you introduced the barbs, or had it been stressed like that before? any other tank mates? water conditions?
tinfoil barb with eat faster then the aro so make sure your aro gets good amount of food daily to continue his growth. I don't think the tinfoil is going to hurt or damage the Aro but may freak him out sometime because they swim fast.