I've found that fruit flies make a good staple food for my Red Devil Crabs, but it's expensive to keep buying a new batch of them every time the substrate starts to mold. Is there a way I can make my own substrate for them?
It's incredibly simple to culture fruit flies. Here's a list of what you'll need for a pretty "bread and butter" recipe:
- An empty container (I use peanut butter jars).
- Instant Potato Mix.
- Powdered Milk.
- Sugar (I use regular, some people use powdered).
- Baker's Yeast.
Mix together the following ingredients with equal parts water:
4 parts of the potato mix, 2 parts of the powdered milk, and 1 part sugar.
Line the bottom of the container with the mixture and sprinkle in a pinch of the yeast. It will seem a little mushy at first, but the potato mix will soak up the water after a minute.
The final thing you'll want to do is make sure the fruit flies have a way of climbing up off of the substrate to lay eggs (they won't lay eggs in it). I use a shredded-up paper towel, but you can stick in popsicle sticks or use straw/hay; just about anything since they're so small and light.
As far as maintaining the cultures, you should be able to notice when the substrate starts to mold after a few weeks (as the substrate is white, and the mold is black). I would say the substrate lasts 5-6 weeks, after which you should transfer any flies leftover to a new container or use them for feeding.
The flies will grow exponentially, so you can start a new culture each week or so, until you are comfortable with the amount of flies being produced.