Clean Easy Way to Culture and Harvest Micro worms (Nematodes) for Tropical Fish Fry, Amphibian Larvae etc.

Microworms are a harmless nematode that make a great food for tropical fish fry like guppies, bettas, and amphibian larvae (newts, salamanders and dwarf African aquatic frogs). They are very easy to culture and provide a good volume of live food once cultures are established. 


  • starter culture of microworms
  • plastic container like a yogurt or margarine container (I prefer the 500mL size as they take up less storage space)
  • lid with small holes in it
  • culture medium (oatmeal, flaked potatoes etc)
  • paper towel cut to size of the container
  • flat wooden stick like a popsicle stick or tongue depressor (or other small piece of food-safe wood)

You may notice that yeast is not on the list! If you are starting with a liquid culture, you do not need active yeast. The yeast is just to start brand new cultures that don't have any food for the worms. Once you have a live culture, the tiny amount of media you have them in will start the bacteria, fungi and yeasts to grow in the oatmeal. That is their food. 

Place a thin flat layer of medium on the bottom of a container. Scoop out a half Tablespoon of live culture (or your starter culture) onto the medium. Place the lid on the container and store in a dark place.

Once the culture is mature (about 3-5 days at room temperature, longer at lower temperatures like in the garage floor at 10C (52 F)), you will see millions of worms shimmering on the surface when you hold the container up to the light. It is time to lay a piece of paper towel on top of the culture medium.

To make harvest clean and simple, lay a wet popsicle stick with one end in contact with the paper towel at one end.  The worms crawl up the wet wood. You can harvest every 12 hours or so.

Cultures can remain active for a week or more of steady harvesting without adding more new medium. When you do add new medium, lift off and compost the paper towel, then add a new layer of medium and a new piece of paper towel. The worms climb up to the top to get out of the stinky mess below. Or you can save some of the seething culture and toss the rest, starting with fresh medium. 

If I have many tiny mouths to feed, I make more cultures to use at the same time.

When the cultures get very soupy and smelly, it is time to make a new one!

Tip 1:
Making sure the entire surface of the culture is in contact with the paper towel will eliminate the growth of fungus on the surface. If some fungus grows on the sides of the container, simply wipe it off with a tissue and compost or flush the tissue.

Tip 2: 
It helps to have at least 3 cultures of different ages going so you have a steady supply of worms for your babies! I try to make mine about 4 days apart.

Tip 3:
Once you have a good culture going, remove a small amount of culture and freeze in a small container. Then if your cultures crash, you can restart one from the frozen sample. 

You can purchase your own starter culture from us!

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