I would like to get D. leucomelas and was wondering if anyone could tell me about how many fruit flies (D. melanogaster) I should provide for it at each feeding.
Also, how often should I feed the frogs, should I get them?
It depends on how many frogs you are getting. I have four juvinile leucs and two azureus, and I usually have 4 cultures going at various stages. Always have more than one culture, even if you only have one frog. They can go sour amazingly fast. I would also recommend getting a backup food source such as springtails or confused flour beetles. Check here:
The old rule I was told when starting out was to make a culture a week per frog, then back off from that as needed. Always at least making 1-2 extra for backups. Unless your conditions are exactly the same (temp, light, humidity, contents of medium, and ff strain) you can not depend on always getting the same results.
Example, I get a much better production in the fall/winter than I do in summer. The temps are only different by a couple degrees, and it is less humid in the summer. I have not yet tested to see if I get less production or if it just takes em a little longer.
As for feeding it depends on how many frogs like Arklier said, and the size of the tank. 3 frogs in a 20 gal will need less than 3 frogs in a 100 gal, as the food is easier to find.
I would feed about 50 flies per frog per day for juvies. Start with this and then if they eat them all within 15 minutes next time add more. I like to see one or two flies in the tank from the previous feeding when I feed. Young frogs you can't really overfeed. Just make sure they don't get stressed out by excess food.
I've gone away for a 3-4 day weekend and have come back with all frogs alive and well. I did however try to give them a heavy feeding the day(s) beforehand and when I have gone away for longer I put a culture into the tank with the frogs and made some holes for flies to escape so the frogs can eat. This has worked in the past. BUT I do feed them every day or every other day depending on availability of food. EVERYONE can attest to their cultures crashing or finishing a bit earlier than expected and new cultures taking a bit longer to get going than expected.
As for number of flies per frog...I have never counted the amount of flies fed to each frog, you just kindof get a feel for it. If your tanks are overrun with flies you will know to feed less. If your frogs look skinny, feed more....If you have done that and they still look skinny be worried.