Fruit Fly Culture Experiment

I started making my own fruit fly culture right from the very beginning. It didn't occur to me that I could by a powdered product off the shelf until I accidentally came across it one day. I thought my only option for buying it was to buy another culture with flies already in it. Fly cultures are expensive, the only place in my city where I have found them charges $14. And they don't always have the type of fly that I want. There are two that are regularly available, the big ones with wings and the smaller ones without. I find the larger flies more useful for most of the things that I feed, and flies without wings are just a little strange. Anyway, months after I started making my own fly culture I tried the powdered repashy stuff.  I don't particularly like the smell of it, but it seems to work well. But how well? I have wondered all along if it is any better than my homemade stuff (the recipe is not mine originally, it was an internet find). So I decided to do a simple experiment. I made up a bash of Repashy, according to the instructions, and placed 3/4 of a cup in the bottom of a deli cup, and then thawed out a batch of my own mixture and placed 3/4 of a cup of it in the bottom of another deli cup:

I left them sitting for a few hours so the temperature would be the same. Then I took some of calcium powder that people use to increase the vitamin content of feeders and added flies.  This allowed me to subdue the flies long enough to count exactly 20 flies into each culture. Now we wait. My questions are these: is my homemade mixture as mold resistant over the long term, which culture retains moisture better, and which will produce a greater number of flies.  Of course I may not have an ideal mixture of males and females in each cup, which could impact the production numbers.

Update:  Well so far the experiment has been a complete disaster.  I always thought that the calcium supplement powder was no big deal to fruit flies, that they just cleaned it off themselves and went on happily with life, but apparently it's fairly lethal to them. They all died, in both containers, except for two.  So, using the same culture, I am going to throw in a much rougher estimate of 20 or so flies into each one, and try again.  Boo.

Update Number 2: Well again this did not goes as expected at all.  My home-made culture did very poorly, developing a lot of mold and killing off the flies.  This seemed very weird at first, because I use this stuff all the time, and have never had any trouble with mold.  I think what's different this time is the small number of flies that I put in.  I think the flies themselves, and their use of the culture, prevents the mold from growing. The repashy of course, produced the usual amount of flies.  Well, I didn't manage to prove that my home made culture is just as good, which was my intention. Clearly under some circumstances it is not. However, it is what I use most of the time, and it works really well at a fraction of the price, so I will keep using it despite the abysmal outcome of my little experiment.