Which Worm Species is Best? Composting Worm Species Comparison
There are four common species used for vermicomposting.
Red Wigglers - Eisenia Fetida
European Nightcrawlers - Eisenia Hortensis
African Nightcrawlers - Eudrilus Eugeniae
Blue Worms - Perionyx Excavatus
Very rarely Alabama Jumpers will be used, but they are not ideal for composting as they don’t do well in a confined bin and they are an invasive species in many ecosystems.
This will just be a quick overview of each species and why you would want to use one over the others.
ALL INFORMATION ASSUMES IDEAL CONDITIONS
RED WIGGLERS
Red Wigglers are by far the most common. They are generally accepted as the easiest composting worm because they are tolerable of many conditions.
Scientific Name: Eisenia Fetida / Eisenia Andrei
Size: 3-4 inches
Appetite: Half their weight/day
Reproductive Rate: 2-3 Cocoons/Worm/Week - 86.6% hatching success rate - 3.3 babies/cocoon
Temperate vs Tropical: Temperate
Difficulty: Easy
Number per Pound: ≈1,000
Sources: https://www.tandfonline.com/doi/pdf/10.1080/02541858.1988.11448096
You should use red wigglers if:
You want an efficient and easy composting worm
You are a beginner
EUROPEAN NIGHTCRAWLERS
European Nightcrawlers are similar to Red Wigglers. There isn't as much concrete scientific information on these guys, so take some of this information with a grain of salt.
Scientific Name: Eisenia Hortensis
Size: 4-8 inches
Appetite: Half their weight/day*
Reproductive Rate: ≈ 1.2 cocoons/worm/week
Temperate vs Tropical: Temperate
Difficulty: Medium**
Number per Pound: ≈400
*My personal experience has been that they eat slower than this, but not by much. This might be because they like to stay deeper in the bin where the food is usually towards the top, but I'm not sure.
**Again, this is based on my personal experience. They seem to be a bit more sensitive to conditions in general, and especially to physical disturbances.
You should use ENCs if:
You plan on using your worms for both composting and fishing bait - ENCs are generally accepted as the best worm for fishing
AFRICAN NIGHTCRAWLERS
African Nightcrawlers are the biggest, and most voracious of all composting worms. I've grown Red Wigglers and African Nightcrawlers about equally.
Scientific Name: Eudrilus Euginae
Size: 8-12+ inches
Appetite: 1.5x their weight/day
Reproductive Rate: .8 - 1.6 cocoons/worm/day - 84% hatch success - 2.7 babies/cocoon
Temperate vs Tropical: Tropical
Difficulty: Medium-Hard
Number per Pound: ≈250
Sources: https://www.ajol.info/index.php/az/article/view/153490
You should use ANCs if:
You know how to keep a worm bin in ideal conditions.
You want to optimize your worm bin to produce castings and process waste at maximum efficiency.
Your bin won’t ever be colder than 60 degrees fahrenheit.
BLUE WORMS - PERIONYX EXCAVATUS
Scientific Name: Perionyx Excavatus
Size: 3-5 inches - usually much thinner/skinnier than other worms
Appetite: slightly less than half their weight/day
Reproductive Rate: 7.7 cocoons/worm/week - 40-60% hatching success/cocoon - 1 baby/cocoon
Temperate vs Tropical: Tropical
Difficulty: Medium-Hard
Number per Pound: ≈1,000
Sources: https://www.ajol.info/index.php/az/article/view/153578
The Controversy of Indian Blue Worms:
It is very rare that anyone sells, let alone buys (intentionally) indian blue worms.
The big nation-wide composting worm vendors - yes probably the one(s) you're thinking of - often sell blue worms labelled as red wigglers. Look for a "composting worm mix" label, or a species disclaimer on the website.
In my opinion, it wouldn't be that big of a deal, but they are also advertising on the same page how red wigglers are the best/perfect composting worm, then selling you blue worms instead. If you truly believe indian blues are comparable composting worms, why are you hiding the fact that you have a mix of blues?
If you couldn't tell, I have also been a victim of being told I was buying red wigglers, but was actually sold indian blue worms. I think sometimes these companies rely on the customers not knowing the difference.
My suspicion is that a big worm vendor received an influx of worms from India (worm composting is huge there), which contained Perionyx Excavatus, which then populated their bins, and the bins of whoever sourced any worms from them as well, which includes other worm vendors.
Why I do not prefer PEs:
They will overtake your worm bin and can quickly overpopulate/overtake other species. They will reproduce closer to their maximum rate when other species won't be at maximum reproduction.
They are very finicky, will leave the bin when the slightest upsets happen, which includes changes in barometric pressure.
They are tropical worms (like ANCs) and will not survive lower temperatures.
Despite anecdotal evidence, scientific journals find that they consistently eat slower (though only slightly) than red wigglers. See the source above.
Not as serious - The way they move gives me the creeps. They don't move like other earthworms.
Why you should pick Indian Blue Worms
They are prolific breeders even in less than ideal conditions. If you are looking for a worm to use as food for another pet, blues could be a great pick.
MIXING SPECIES
If you do not mind mixed species there is some benefit in that however the conditions are in your bin the worm species that handles it best will reproduce and populate your bin. There are other minor advantages to each species that you can get by using a mix.
If you want to keep a good population of red wigglers or european nightcrawlers I would avoid adding blues to your worm bin as they will outpopulate other species.
CONCLUSION
There is no best worm, it totally depends on your circumstances and your goals. For beginners, I always recommend the red wiggler. They are going to be the easiest worm for an inexperienced worm farmer.
Find useful guides on vermicomposting, including how to start a bin, at www.utahbioagriculture.com/guides