A vessel with a long neck is used. We have found a neck with a straight (parallel) inside wall is better. It will make it easier to remove the filter material later.
Using a funnel is a good idea. Vinegar on the counter is one thing, the floor another...but getting it on your hands makes your co-workers think you've been snacking on salads.
Fill the container to the bottom of the neck with culture material. You can leave any mulm in the material as the process will remove the eels and not the material.
Use a small amount of fiber filtering material (we use poly material) and make a "wad" of the material that will loosely fill the bottom of the neck like...
this. Note there can be small gap between the top of the culture and the bottom of the fiber. We like to push the material into the neck so that is just barely touching the culture material. If you push the fiber too far you will regret the move. You will have to put another piece into the container and later remove the first also. If you do push the fiber too far don't worry about taking it back out until after you have run the cycle of harvesting. The fiber will not change the results.
Gently fill the neck with system water. The small gap below the fiber will fill with water and mix with the culture. The water above the fiber will stay clear. You might want to check the pH of the water above the fiber at the time of actual harvest ( in eight hours or the next morning).
You can remove the water above the fiber and feed directly to the larval fishes. The nematodes seek the O2, traveling through the fiber to reach the surface. This harvest method will remove the vast majority of the eels from the culture. We have found that after about 2 days (sometimes in a single day), the culture will yield no significant number of eels (it is nearly completely harvested). It will be necessary to let the culture re-grow itself over some period of weeks. The culture material can be reused numerous times. The small amount of water that is added in the process is insignificant.
The results the next day should be a cloud of nematodes in the clear water above the fiber material. It's a pretty simple technique.
"We grow food not bait"
The Bug Farm
San Rafael, CA 94903 USA
© 2001, 2002 2003, 2004, 2005, 2007, 2009 J. Atchison