That is an awful lot of small dats in with that aro with no hiding place. Although I like dats as tankmates for aros, aren't they bit bit too small? I am sure a hungry dat would pick them off.
I agree with you and said the same thing to Tam (owner of the fish). He assured me that his aros don't eat the dats. I asked him what he feeds his fish and he told me live barbs. Live barbs (of various kinds) are the default feeder fish in South Vietnam, where they are easy and cheap to raise. I'll ask Tam for a feeding video in future. Tam operates a kind of home-based business, so all of the dats are actually for sale. Tucked in there somewhere are 4 CT (Cambodian Tigers). He told me that true ST are around too, but not for sale.
Here is another video to share. This Merlion Ultimate Chilli Red also belongs to Tam.