same here i mainly feed my open and closed brains mysis and brine shrimp...and they will show there tentacles during lights on/off or when i turn off the water pumps... i have tried given it krill and will do just great but of course i only give hime 1 at a time...

my open brain has two mouths but i think that aslong as u feed one mouth the nutrition/food ends up in the same place, they just tend to have several openings to be able to get food , that is what i think..