Well here's my 2c. To be on the safe side rehome the tang first. Meanwhile, give the colini a feeder acan or trachy in the sump (not kidding).
My male took ages to recognise food in the water column, but now, a year later he assertively eats macro from a veggie clip. OTOH the little female quickly learned to compete, so I guess you could get lucky.
Goldens are usually picking at food in the shop... at least the ones from Vanuatu which seem to be collected well. That said, I assume your colini is from cairns , so he's been handled pretty well. Let him temporarily snack on the microfauna around the acan and eat it too if need be. Meanwhile try leaving assorted food on the ground nearby. After he gets the hang of frozen you can give similar food in the water column.
hth and good luck!