Vermicomposting 101: Should I Mix Worm Species in My Worm Bin?

As the season swings into gear, I am commonly asked the question “Should I mix earthworm species in my worm composting bin?”

Normally, people are interested in mixing red wigglers, European nightcrawlers, African nightcrawlers, and possibly Indian Blues.

I have my own thoughts about that, but before I give you my general recommendations, let’s explore the cases for and against mixing species.

This article is part of a “Vermicomposting 101” series of posts aimed at helping the beginning vermicomposter. The read other “VC101” articles on how to start a worm bin, how to choose worm food, how to maintain moisture, and the differences between composting and vermicomposting, please visit the Vermicomposting 101 section of this site!

Why to Mix Species in Your Worm Bin

You Want To Mix Species to Vermicompost at Different Depths

In general, European nightcrawlers are believed to burrow a little deeper than red wigglers and Indian blues and African nightcrawlers are believed to burrow a little deeper than Euros, so the thinking is that a more uniform processing of waste is more likely with more species.

As I am pretty much a run-of-the-mill red wiggler man, I do not have a particular opinion as to whether this is true. If it is, then this is a fine reason to mix species. But I have also seen red wigglers way deeper in a wet, compacted worm bin than I thought I should find.

Mixed Worm Species Insure Against Swings in Temperature

Each worm species has its own temperature range where it demonstrates its greatest efficiency. European nightcrawlers generally enjoy slightly cooler temperatures than red wigglers would find ideal. And Africans and Indian blues need warmer temperatures than the red wiggler.

So it might make sense to include a variety of species so if you have weather patterns like Philadelphia which goes from well digger’s ass cold to Satan’s armpit-level hot and muggy in an instant.

At either of those ranges, at least one of your species is happier than the others, although it’s worth pointing out that none of them will be happy at the extremes.

Our Diversity is Our Strength!

Like most ecosystems, a greater diversity of organisms portends good things. Much like the temperature argument above, a robust variety of species may withstand shocks to the system better than a single species.

Applying this principle to your choice – or choices – in worm species might make sense if you think several worm species is better than one.

Why Not to Mix Worm Species In Your Worm Bin

Mixing Worm Species Sacrifices Reproduction Potential

Contrary to some wives’ tales, worms cannot interbreed or hybridize.

But this does not mean that worms are unaffected by the population around them.

Worms are excellent self-regulators and will slow their reproduction when the population density reaches a certain level, ultimately maxing out at 2-3 lbs per square foot (maybe a bit more), depending on the conditions in the bin.

Below a certain density – I’m not sure what it is, but I reckon it’s around 1 lb per square foot – the opportunities for a love connection are reduced as well, so if you stock a 4-square foot bin like the Urban Worm Bag with 1 lb of red wigglers and 1 lb of European nightcrawlers, your worm density may be 1/2lb per square foot, but the density of the worms that can actually breed with one another is 1/4 lb per square foot, less than optimum if you’re trying to grow your population quickly.

It’s More Expensive to Buy Multiple Species

Purchasing two breeds normally means two packages from your supplier.

One two-pound package will ship for way less than two one-pound packages. For instance, 2lbs of red wigglers purchased at Urban Worm Company is nearly 30% less than buying one pound each of red wigglers and European nightcrawlers.

You May Already Have Multiple Species In Your Bin!

Reds-vs-Blues-Featured-Image

Gasp! Well it may be true.

Worm bin owners may be surprised to know that what they thought were purely red wigglers in their worm bin were actually a different species called the Indian Blue. Although similar in form and function to a red wiggler, the Indian Blue mixes its voracious composting ability with an annoying tendency to attempt a mass escape from the bin for seemingly no reason.

This helpful article will teach you the similarities between “reds” and “blues” and will help you to be able to tell the difference!

My Thoughts: Multiple Species are Fine, But Not Necessary

There is absolutely nothing wrong with multiple species in a worm bin, but I can’t find a compelling reason to say you should. Of the arguments for intentionally introducing mixed breeds in your bin, the depth issue is the most convincing.

But I’m not convinced.

The species purported to burrow the most deeply is the African nightcrawler. But it is still an epigeic, top-feeding species and despite its size, I don’t think it is an appreciably better burrower than the red wiggler.

And this may sound like heresy, but the diversity argument isn’t convincing either. A healthy worm bin has huge and diverse microbe population. While diversity is generally a good thing, I don’t consider a different flavor of worm poop to be meaningful diversity.

So while I fully support anyone who is experimenting with different breeds, there’s nothing screaming at me that says it’s a better way to vermicompost and the purported upside to me just doesn’t outweigh the added cost. Take the money you would have spent on two separate pounds of worms and just buy 3 lbs of a single species like the red wiggler for the same price.

If you liked what you read here, I invite you to join my e-mail list below and read the rest of my Vermicomposting 101 Series.

18 thoughts on “Vermicomposting 101: Should I Mix Worm Species in My Worm Bin?

  1. Steve, I do see where a number of folks combine red wiggles & African nightcrawlers. One aspect to consider is the actual physical difference of the worm castings. Red wiggle castings are a finer, smaller casting (similar to clay particle size), whereas the African nightcrawler’s casting is larger, (similar to sand particle size, that actually feels like sand when dried out). This aspect may seem ideal to folks even though the water-holding capacity/water permeability of both species is virtually the same if raised in the same environment. Similar to having a slit loam soil rather than an all clay soil. Folks are producing what they consider a more premium worm casting.

  2. I agree, I’ve found no benefit whatsoever to having multiple species in a bin. In fact it seems to result in an overall lower worm density. Perhaps the multiple species results in lowered reproduction capacity of all species.

  3. My mixed bag seems to be doing well I’ve got just about every kind of worm in there red wigglers, European nightcrawlers, Indian blue worms, Alabama jumpers, and whatever random worms I gathered from my yard. It has been about 3 months since I mixed them all together I guess I should probably harvest some castings soon I tried to open the zipper on the bottom today but it was stuck maybe because it just rained recently. My mixed bag is also basically completely full and has fallen over a couple of times, now I have it wedged against a log. It also ripped a little on top probably because I had overfilled it so much with heavy bedding material. I think I’m going to build another worm bin and split this one up because there is just way too much weight in there, maybe I will just go through it and try to pick out all the worms and see how many there are and try to tell how roughly how much of each kind I have.

    The individual red wiggler and European nightcrawler bags are also thriving but I didn’t put nearly as much material in those and mostly used just cardboard and food scraps.

    I’ve kept them all outside under a tarp surrounding a wire frame hot compost pile that is cooking at about 140 degrees Fahrenheit right now.

    I got a heavy duty 16 sheet microcut shredder which works great for cardboard and I have been adding some to the worm bins and a lot to the hot compost pile. I’ve found that it really helps when you need to regulate the moisture of the worm bins or the hot compost pile if one gets too wet adding dry microcut shredded cardboard absorbs the water quite well.

    1. *Forgot to mention I had also put the African nightcrawlers as well in the mixed bag.

  4. Any support for having multiple species to provide bait? Some fish don’t like big worms. It would be great to throw some Canada crawlers in the bin and just take a dozen or so at a time.

    1. You could try this, Norman, but the Canadian nightcrawlers will not thrive in a vermicomposting bin.
      SC

  5. I live in South Africa….I only had a bin of red wriglers ….then we had to move but the worms had to stay …I had no place to keep them . but I managed to drop a few into my potplants…some of which had lots of unfinished compost in the bottom and I do keep feeding my plants with leaves or whatever is at hand because I can’t have a compost heap . So next I started putting down 750g coffee cans …with holes knife punched round and bottom ….in the ground with foodscraps in lids sticking out the ground ….and keep filling as it decomposes to make compost …or at least feed my plants …….next thing I find red wriglers crawled or slithered back into the cans very happily and if I find some I also put them in there …and they started breeding……then I realised they need a better home and I harvest them to put into the better home .( worm farm) ….then I notice but some worms look different and realise …I have African night crawlers ….lots ….of both ….but now some worms look more like a mix of the two worms ….is that possible ?.or do juvenile ANC worms maybe look like …red wriglers ? they seem to be very happy all of them together . And I did not pay one cent for them …I just feed them and they come to mamma.

    1. I started with red wigglers and used a potting soil with ammonia. I am still upset with myself for that mistake. I immediately changed the bedding and added more worms. Only I added earthworms again a mistake on my part. I don’t know if I should separate them or leave them as is. I would greatly appreciate any suggestions to help keep my worms happy and alive.

      1. Hi Michelle,
        As I understand it, you added regular garden-variety earthworms to your worm bin this last time correct? If so, it’s not a huge deal. If your bin has been rehabbed with more compost worm-friendly bedding material, then adding red wigglers in there with the existing worms will be just fine. No need to remove them.

    2. Hi Sam,
      It should not be the base bedding fore sure. But you might be able to use it as an additive, in moderation of course!

  6. I’ve had my compost tumbler outside and my urban worm bag inside all winter. I live in Philly so it’s pretty warm here by now. A bunch of garden worms (night crawlers maybe?) have found their way into my tumbler and Id like to introduce some of my thriving red wigglers into the outdoor bin to increase production. Do you think it will be a problem ?
    (And Hi Steve! I’m a big fan! Thanks for all you do!)

    1. Hi Karenina! I would not add composting worms to an enclosed tumbler. If the tumbler gets hot, the worms won’t have anywhere to escape to! Thanks for the kind words! 🙂

  7. When I started my worm bin 4/15/21 I purchased initially 100 red wigglers and soon figured that is wasn’t enough to compost very quickly so on a recommendation from a gardener friend I purchased 2000 red wigglers from Uncle Jim’s but i soon realized that had not received 2000 worms and they were mostly blue worms. The Blues are reproducing quickly and I am now moving half to a second bin. I found that I have to leave a light on to keep the worms from wandering again. Your article answered my question if the Blues would Mate With the Reds. Thanks for the information. The next time I order worms I will weigh the worms upon arrival and check to see if I got what I ordered.

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