I raise my fruit flies in 1/2 qt. deli-cups with a media and protocol from Saurian. I restart a new culture every 2 or three days alternating between two different species of flies. D. melanogaster and D. hydei are different sizes, the melanogaster being smaller, more suitable for the thumbnails and the hydei fill up the larger frogs faster. But I have a lot of frogs, so you may not have to renew your cultures as often as this for a constant supply. Once in awhile cultures will crash for some reason, so I like to have extras on hand.
To feed, I just sprinkle a bit of vitamin powder and paprika (for the orange and yellow frogs) around the bottom of a clean deli-cup, then tap or "jump" the fruit flies from the culture into this, (off the edge of the culture cup at about a 40 degree angle,) swirl them around in the dust and feed. There are always fruit fly escapes, but you just get used to having them crawl in your ears at night. I like the deli-cups for feeding, because you can hold them at an angle to the tank, tap and maniupulate the dusted flies to the front to jump to their demise without dumping in the excess vitamin powder.
Everyone seems to have his own technique. You just get the feel of what works.
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Patty
Pahsimeroi, Idaho
4 D. auratus blue
5 D. galactonotus pumpkin orange splash back
5 D. imitator
6 D. leucomelas
4 D. pumilio Bastimentos
4 D. fantasticus
4 P. terribilis
4 D. reticulatus
4 D. castaneoticus