Same problem, great question.
I fed my girls pellets for a while, then started feeding them blood worms, they scarf them down now. Before, 2 minutes was reasonable, it was like 1-2 pellets in a 2 minute period, now they can plow through a pile of blood worms in 2 minutes as long as it keeps snowing!
I have my one female in a hospital tank, and she can eat as much as i feed her. I usually give a small pinch each, one per individual, in their own areas.
However I like to always drop food in one place, as they all come out to one area and are all (for once) in a tight group, relaxed and enjoying eachother withought hiding on thier own!
How much is too much?!?