How big is the tank? How bout a full tank shot? If you really want to do Mandarin's, I would look in to a 'copepod hotel' They're these little contraptions that you can buy or make to house pods. Fish can't get at them and it's a good tool that you can use to ensure that there's always a population in the tank for things like mandarin's and other dragonets. Buys some pods, get a 'hotel' or two and that will help jump start and ageing the system for those very specific eaters.