Fish food Guest posts

How to set up a blackworm culture

February 12, 2018

Live worms are one of the most nutritious foods for small to medium sized fish, and are accepted by all but the pickiest. They are rich in proteins, fats and vitamins, which makes them an excellent food for both encouraging breeding and growing fry.

There are two types of freshwater worms common in the hobby. Tubifex worms and California blackworms. Tubifex worms are smaller and pinkish white in color. They require very large amounts of oxygen to survive, which necessitates cold, shallow waters. Blackworms, on the other hand, grow larger and are a darker brown-red to black. These are are much more tolerant of varying conditions, in some cases even establishing small colonies in your tank!


In this guest post, Chris Takagi shares his method for setting up a successful blackworm culture. Thank you Chris!


Starting a blackworm culture

How you decide to culture your worms depends a lot on how intensively you plan to harvest them. If you think you’ll only use them as occasional treats for your fish, you can simply grow some in a 5-10 gallon tank with dwarf shrimp and no problems.

If you are using blackworms as a staple food, for breeding fish or feeding pufferfish you’ll need a dedicated tank, as intensive cultures produce a lot of waste. The worms can survive very well on very little food, but the more you feed them, the faster they’ll grow.

To start out, you’ll need: 

  • An aquarium you’re not using, or a plastic food container
    o You can also use a bucket, but increased footprint is better
    o The bigger it is, the more you can feed them
    o I use an old five gallon tank to feed 4 Amazon puffers
  • Some sand or gravel
  • o About enough to cover the bottom of your tank to an inch deep
  • A filter
    o A sponge filter is sufficient and cheap, but any filter that can work in less than 6 inches of water is good
  • A starter culture
    o Ask your LFS if they have blackworms. If not, you can probably order some online
  • Some organic compounds (food)
    o These worms will eat literally anything
    o Don’t feed them diseased fish, as that could spread disease to your fish

Other helpful but not required items are:

  • Plants
    o Plants help remove waste from the water and the worms will eat the dead leaves
    o Emersed plants grow faster than submersed ones
    o Pothos and Java moss are good choices
    o Low light plants are better, because the worms are less active in bright light
  • A turkey baster with clear sides
    o Lets you suck up clumps of worms for easy harvesting


Setting up your blackworm culture

Pick a spot where you want your culture to be. Keep in mind that the worms don’t like rapid temperature changes and can’t survive below freezing. The culture is also super ugly looking, so it’s probably better to keep it out of sight from display tanks.

Once you’ve chosen a spot, add the sand/gravel and filter. Fill up the tank with dechlorinated water, to no more than about six inches deep. The shallower the tank is, the more oxygen the worms will get, but you can substitute air-stones for shallow depth. Then let the filter cycle, or else ammonia will build up extremely quickly.

Once the tank has cycled, go and get your starter culture. It will probably be refrigerated, so don’t plunk them into the tank immediately. First, warm the worms up more slowly in the air (if your starter culture wasn’t refrigerated, skip this step). After they’re about room temperature-ish, pour them into a small container, and cut the blob of worms in half, then in half again. They will regenerate heads, tails or both within a few hours, and this jumpstarts the culture’s population.

Maintaining your blackworm culture

After you’ve cut the worms, you can drop them in the tank and feed them a bit. I like to feed mine a staple of sweet potato slices and old fish food, along with plant trimmings and dead leaves. After a few hours or less, you should see the worms clustering around the food you’ve added, tails in the air, and heads buried. If they start trying to climb to the surface, that means they need more oxygen. You should increase aeration and possibly reduce the depth.

It will take the halved worms about 2-3 weeks to grow back to full size, depending on feeding rate and temperature (they grow fastest at around 70 °F/21 °C). Harvesting the worms is as simple as sucking them up with a turkey baster

Things to keep in mind

  • The worms will fragment and reproduce on their own, but if you ever want to speed up the
    process you can collect a cluster, cut it in half, and then return it to the culture bin.
  • Food can sometimes start rotting in the tank. This is totally fine, the bacteria feed copepods
    and also the worms.
  • Sometimes you’ll find little leeches in your culture. This is also not a problem, the fish will eat these too.
  • Copepods will abound in your culture tank. If you drop the oxygen a bunch, they’ll swarm at the surface. You can collect them and use them as fry food
blackworm culture

Chris’ own blackworm culture.


If you have any more questions about setting up a blackworm culture or want to share your own experiences, don’t hesitate to leave a comment below!

Want to culture more live fish foods? Have a look at the articles on culturing Daphnia and culturing grindal worms.


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