Why don't you feed fruit flies directly into the frog's enclosure and use feeding containers? Also; are you using food supplements (CA/D3 and vitamins) to dust flies? It is very important to do so during a froglet initial growth stage. Sample schedules in here: http://www.frogforum.net/food-feeder...schedules.html.

Here is method I use to feed all my darts in couple minutes. You will need 2 empty plastic 32 oz. containers; your fly culture; a sink to catch any escapees. In one container you add your food supplement according to schedule. Tap you FF culture and open lid; tap again. Tilt FF container 45-60 degrees (FF like to climb) and tap them into empty container held by other hand. If they start climbing up before getting dusted (slows them down) tap that hand to mix them up. Once you get the desired amount; tap both containers, place one with dusted flies down in sink, tap the culture and place lid on it.

Now tap lightly the container with flies until all are well dusted and tip it while lightly tapping to get dusted flies into the second empty container. The idea is to get all flies out while leaving supplement dust behind. Once separated (a bit of dust will always get through - no worries) then just tilt the flies into your frog's enclosure. You want to add enough flies so froglets eat to satiation.

It sounds complicate as you read and first couple times; but once it becomes routine, you can feed many frogs from different cultures in a couple minutes .