My nile monitor doesn't seem to have a taste for much ....he hasn't grown as much as he should have by now. He's still quite small. I was betting on a parasite but his stool is fine. He's eatting has proper heat and lighting. Maybe I just got a dwarf lol!I'm surprised your nile monitor doesn't like them more; I have a savannah monitor and the reason I got him was to keep my roach numbers in check. He eats them day and night; any species. He will eat 20 or more subadult B. craniifer sized roaches a day if I let him and he's only half-grown. Savs are supposed to have a diet primarily of grasshoppers, walkingsticks, mantids, and presumably roaches in the wild as opposed to vertebrate prey so that might be why he's so keen on eating them.