It stopped eating market prawns shortly after I rescued it, so I fed it a batch of feeder fish to get it eating again and then started it on crickets and superworms after that. It's only been eating them for about a week. It was eating the odd small piece of market prawn, but not enough to keep it going so I gave in and fed it mealworms. The majority of that white stuff seems to have disappeared, so I'm assuming it was just do to a slime coat issue. Now the question is what caused it. Maybe the fact that it moved in to the tank about 2 1/2 weeks ago and it's still stressed?