One of the most common variables overlooked in culturing fruit flies is the surface area used. I have seen cultures with everything under the sun used as surface area. The two most common sources of surface area in fruit fly cultures are coffee filters or excelsior. Each has their pros and cons.
For best results, coffee filters need to be folded so they look like pie slices. I will fold 5-6 together and push the point into the media. Coffee filters will absorb excess moisture in the culture media and therefore act as a moisture barrier, so they are less likely to dry out or become soupy. The downside to coffee filters is that they can get too wet and will collapse and bury the fruit fly media and hurt production.
Excelsior has been a long time staple in fruit fly cultures. It creates tons of surface area and takes less time to use (just grab a handful and throw it in the culture). The downside is that is quite messy to use as some of the fibers will inevitably fall out with the flies when feeding.
All cultures sold at Josh’s Frogs will be setup with excelsior.