I'm still a little new to keeping fruit flies, but I think I've figured it out. I started with the smaller fruit flies, which I probably shouldn't have... I'm still waiting for more Hydei's in the mail from Wormman.com. But I got 12 wide mouth glass jars to do it in for now (more later). I use a recipe for the medium that was as simple as possible, involving 8 cups of potato flakes, 1 tablespoon of powdered sugar and a third cup of yeast (I used the kind for bread machines cause that's all I could find but it works). I mix all these dry things together. Then when ready to make it wet, get about an equal part of this dry mix and mix it with an equal part of a 1.1 water to vinegar ratio. So it would be something like 1 cup of the dry mix, 1/2 cup water, 1/2 cup vinegar. You may need to add a little water or dry mix to get the consistency right. It should be like slightly thick mashed potatoes. I've tried it a few ways, making it thinner and thicker. Too thin and the bugs stick to it and it gets runny after a week or so, too thick and the top layer dries and makes it hard for the maggots to move around in. I also tried it using only water (no vinegar) and it worked ok for a week but after that there was a layer of what I assume was water on top of the medium, probably killing all the eggs and eventually they all died. I think the vinegar keeps the consistency better and keeps the two liquids from separating. I get a small scoop of this mix and stick it in a CLEAN CLEAN CLEAN jar. I make it a little less than an inch deep. It shouldn't even settle... It should kinda just clump up at the bottom. I tap it on the floor and it'll make it level. Then I cut a few pieces of fiberglass screen about 2 inches wide by 4 or 5 inches long and put them in there pushed into the medium standing vertically. They can space themselves out on that and get a place to crawl. After about 2 weeks with the small flies you'll have more flies, and with Hydei's it's more like 3-4 weeks. You need to use some sort of cloth on top of the jar, like a piece of a T-shirt or a rag or something. I used a paper towel and somehow they got through it in 3 or 4 different jars, I don't know if it got wet and came apart or what. I keep them at room temp or cooler. I think at extreme temps, the meduim acts up. I have much more flies right now than I know what to do with and if anyone in the area wants any let me know. I'm just watching them die right now as nothing I have eats them. I'm probably producing around 50 flies a day right now in a few small jars. I have a few larger colonies in larger jars that haven't turned into flies yet, but when I get more Hydeis, I'm getting rid of all these small ones. Let me know if any questions. I might know the answers maybe not.
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Tyler Stewart
Las Vegas NV