3 Methods I Use to Separate European Nightcrawlers From Their Castings (And 2 I'll Never Use Again)

What I Do When My Worm Castings Look Like This

This is a handful of (mostly) finished worm castings.

Other than a few bits of organic matter here and there, the castings in this bin full of European Nightcrawlers are ready to be harvested. It's taken about 3 months to get my vermicompost to achieve this beautiful, rich "chocolate cake" consistency but it's right on time to fertilize my warm-weather crops when I plant them out in the garden. The only thing that I have left to do before I can use my worm castings is to separate the worms out of them. 

These are 3 methods that I use to separate compost worms from their castings, and 2 methods I'll never use again:

Method #1: Horizontal Migration

My European Nightcrawlers would migrate from the finished castings into the newspaper bedding.

Horizontal migration is a popular technique used by worm breeders to get compost worms to come out of their castings naturally. It's the least stressful method for the worms because they willfully leave their castings to get to a fresh food source.

The only real downfall to using horizontal migration that I've found is that it takes weeks to get the worms to migrate and stay put. (I don't have that kind of time on my hands so the picture above is for demonstration purposes only. I've used the method. It works well. But if time is of the essence it just isn't convenient.)

How to Set Up a Worm Bin for Horizontal Migration:

1. Rake everything in the worm bin to one side of the bin.
2. Fill the empty half of the bin with fresh bedding.
3. Only feed the worms on the side of the bin with the new bedding.
4. After 2 to 4 weeks of feeding, most of the European Nightcrawlers will be out of the castings and living in the new bedding.
5. Remove the castings and fill the empty space with bedding. ( Feed anywhere in the bin now.)
6. ( Optional) Screen or sift through the castings for any remaining worms and cocoons.

Method #2: Bait and Pick

There is a butternut squash stem sticking up in the lower left-hand corner of the bin. The 3-inch piece of squash attached to it (under the castings) is the bait source that I use to collect worms by hand.

I've been using this method in this bin for a while now. It seems to work slightly faster than trying to get them to migrate. It does cause the worms a little more stress though.

Choosing to use the "bait and pick" requires a second bin to be set up in advance to put the worms in when they come out of the castings.

How to Bait and Pick Compost Worms Out of Finished Castings:

1. Feed the worms a small amount of food in 1 corner of the bin.
2. Pick worms from around the food source daily.
3. If there isn't any food or bedding left anywhere else in the bin, most of the worms will be removed from the castings in a week or 2.
4. (Optional) Screen or sift through the castings for any remaining worms and cocoons.

Method #3: Screening

In this picture (which was taken mid-shake) is my 1/4 inch mesh basket that I use to screen my vermicompost.

Screening finished castings to get remove compost worms is the fastest method that I've used by far. It does cause them a bit of stress though from getting bounced and shaken around.

How to Screen Compost Worms From Finished Castings:

1. Place handfuls of material from the bin on a screen with 1/4 inch mesh and hold it over a tarp or empty storage tote to catch the castings.
2. Gently shake the screen back and forth over the catchment container until all that's left on the screen are worms and any unfinished bits of organic material. ( Smaller worms may fall through the mesh, but can be easily picked out.)
3. Repeat until the bin is empty.
4. (Optional) Repeat steps 1 through 3 on the screened castings with a 1/8 inch mesh screen to separate out most of the cocoons.

I'll Never Use These 2 Methods On European Nightcrawlers Again

Both of these methods of separating composting worms out of their castings are forms of induced migration. One method works very quickly but can be really dangerous to the worms and the other one is good for harvesting castings from other types of worms like red wigglers but is almost useless on the European Nightcrawlers in my bin.

Method #1 Vertical Migration

Vertical migration is very popular with worm breeders who have flow-thru and stacking tray worm bins. After the worms start to build up a good amount of castings, a new layer or tray of bedding is added and all food is added to the new layer. This entices them to move into the new bedding and the castings underneath can be harvested.

This was the very first method that I used to try to lure my European Nightcrawlers out of their castings and I failed miserably. I tried to feed them all near the surface and "mine" the castings from underneath the worms. I was successful in getting a lot of them to migrate out of the castings and into the new bedding, but European Nightcrawlers seem to like to live deep in the bin and there were still a lot of worms to be screened out of the compost. 

Method #2 Thermal Migration

Thermal migration is downright dangerous for any kind of composting worms but works extremely fast on the ones who survive it.

The idea behind thermal migration is that an extreme temperature change is created at one end of the worm bed and the worms go to the other end to get away from it. I buried a frozen water bottle in the castings at one end of my bin and harvested from that end after a few minutes. I also harvested quite a few dead worms of all sizes who froze to death because they couldn't get away fast enough.

There are other ways to induce thermal migration in a worm bin, but that time was all it took for me to not be interested in experimenting with them. It's cruel and unnatural, and the 3 methods I listed and explained above work just fine for me.