There is no real set feeding amount. Just feed until you know they are full, but that seems like a good amount to beef those guys up. Just remember to keep up with the water changes when you're feeding very frequently like that.
If you want to beef them up, make sure you vary the diet and keep pristine water conditions. Try some frozen krill, market shrimp, black worms, or even smaller earth worms (just make sure you let the worms purge their system first before feeding).