What You Need to Know Before You Buy Compost Worms

Before you buy compost worms for your worm farm, there are a few things you need to consider. This includes:

  • understand what worm species will suit your worm farm
  • how many worms do you need to get
  • where to go to buy compost worms near you or online

Species of Worms

There are 3 kinds of earthworms, grouped based on their ecological behaviour.

  • Epigeic / Epigean earthworms – live at or on the soil surface that is rich in organic matter (e.g. leaf litter, manure etc)
  • Endogeic earthworms – live in the soil and burrow horizontally
  • Anecic earthworms – live in the soil and burrow vertically

There are about 6,000 species of earthworm. Worms that you find in your backyard are most likely unsuitable for vermicomposting. Epigeic earthworms such as Red Wigglers, are the worm of choice for quick composting in a contained area.

Red Wigglers are the most popular species of worms for vermicomposting. This is because they are:

  • prolific breeders
  • very tolerant to varying environment conditions (more than other species)
  • don’t mind the occasional disruption or handling (unlike other species)

Worms referred to as nightcrawlers only come to the surface at night (hence the name :)).

Here’s a comparison of the most common species of earthworms used for composting, and their suitability for different environment conditions:

Worm Species Names Description Environment Conditions
Eisenia Foetida or Eisenia Andrei Red wiggler, manure worm, red composting worm, tiger worm, brandling Small, red / brown color Most adaptive to moisture and temperature extremes than other species.
Eudrilus Eugeniae (Anecic) African nightcrawler Large, grey / purple color Cannot tolerate extreme cold and dislike disruption and handling.
Eisenia Hortsenis European nightcrawler Medium, darker color than Red worms Prefers cooler temperatures and can tolerate a wider moisture content range than other worm species.

Dislikes acidic conditions.

Perionyx Excavatus Indian blue, Malaysian blue Small and thin with blue / purple sheen Prefers warmer temperatures between 21 ad 30 C.

Cannot tolerate extreme cold and dislikes disruption and handling.

Combining Species of Worms

Worm suppliers usually breed worms in outdoor worm beds called windrows. This method cannot  guarantee that all of the worms will be of the same species. That’s OK because combining different species of worms can improve the overall strength and resiliency of your worm farm. Some worms do better in warmer weather, whilst other species do best in colder weather.

Worms cannot cross breed, and can only breed with their own species. So over time one species can begin to dominate and even out populate any other worm species in the bin.

Quantity of Worms

The amount of compost worms you will need depends on two factors:

  • how much space is there available in the worm bin
  • how much left-over food waste do you have

To get an idea of how much food waste your household produces, do the following for 1 week:

  • collect food waste that you would normally feed to your worms
  • at the end of each day, put all food waste in a plastic bag and then weigh it

After 1 week, you can calculate your daily average food waste.

You can typically buy worms by 250, 500, 1,000 and 2,000 amounts. Worms eat about half of their body weight each day. But note this rarely happens straight away as they need some time to settle in and get used to their new home. A rough weight estimate for 1000 worms is 1 pound or 500 grams. So if you average 500 grams of food waste each day, then your system will need about 2,000 worms.

Worms populations are self-regulating. Assuming favorable environment conditions and sufficient food supply in the worm bin, your composting worm population will expand to fit the space available. In very general terms, a Red worm population can double in number approx every 60 to 90 days.

Where to Buy Compost Worms

You can buy live worms online and have them delivered to your home. Be aware that the journey for your worms may be disruptive to them causing stress. When you receive the worms, make sure they have some fresh bedding. Leave them for a day or two to settle in before giving them any food waste.


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