your O is baby, you can use small shrimp for now. you'll have to cut into bite sizes now anyway. they have some stringier parts than worms. I tenderize with shallow crossed slices or he spits tough pieces out.this will sound dumb..what is a prawn?
LOL, true. nothing like some love sacrificial dithers to perk up an O.Very nice looking O!
It might help loosen him up a little to have some sacrificial dithers. Some large live bearers or some giant danios might make him feel more comfortable....
so, he didn't even grab & toss the cut wiggly worms?
Higher-end tank temperatures usually increase appetite.