How to Culture Microworms

What You Will Need

• A Plastic Container With a Top (Margarine Containers are Great for This).
• Pure Oatmeal
• Dry Yeast
• Microworm starter culture

If you’re serious about breeding fish, then at some point you should consider starting a culture of microworms. These tiny worms are the perfect food for many species of newborn fry and their wiggling motion in the water triggers a fishes hunting instinct. If you don’t offer newborn fry a source of live food, you will often have a very high mortality rate among the fry.

These tiny worms are actually a nematode, and they grow up to around 0.1 inch (3mm) in length. They have a whitish color to them and most will clump together in long strands of worm in the culture. Each culture will hold hundreds or even thousands of microworms, and you can easily see them climbing the sides of the cointainer that they are kept in.

What makes microworms one of the best cultures for fish is that once you have the culture going, they are incredibly easy to maintain and only need maintenance every few weeks. This is in sharp contrast to Daphnia and blackworms which need constant attention and often crash for no reason. A single culture of microworms can easily last for 4 weeks before it needs to be changed, though I would recommend that you keep several cultures going in case of unexpected crashes.

Getting Started

To begin with, thoroughly clean out the plastic container that you are planning to keep the microworms in. Make sure that there is no soap residue, and that is has been rinsed in water several times before adding anything to the container. At this time you should also add some air holes to the cover, but keep them as small as possible to help keep pest insects out.

After the container has been prepared, you should add about ½ inch (1.2 cm) to ¾ inch (1.9 cm) of dry, plain oatmeal to the bottom. Then add some water to the oatmeal, making sure that the oats are damp, but not watery. Thoroughly mix it together so that all of the oats are wet, making sure that there is no excess water.

Once you are satisfied that the oats are damp all the way through, you should add a small amount of yeast to the top of the oatmeal. It’s better to err on the side of caution and add too little, rather than too much, and you really don’t need much in the way of yeast to start with.

After you’ve done that, you’re ready to add the microworm culture to the container. The microworms are usually pretty easy to pick out, and their coloring seems to almost shimmer under a light. Use something soft like a Q-tip or paint brush to move them, since anything hard will likely injure or kill them.

Very softly spread the microworms over the top of the culture, and this is where it’s very important that it’s not too wet. You want them resting on the top of the culture, and not sinking into it. After the starter culture has been added, you should immediately cover it. Pest insects like fruit flies can become a major problem for microworm cultures, and a way around this is to fill any air holes with cotton or something similar that will still allow air in the culture, but keep the pests out.

Within a few days, you should start to see hordes or tiny microworms scaling the sides of your culture. It’s at this point that you can start harvesting them, and it’s as simple as wiping them off the side with a finger and placing them in your aquarium. I tend to use glove for this, but it’s up to you how you want to do it.

After about 4 weeks, the culture will start to smell. This is the signal that the culture needs to be replaced, as you won’t be able to keep it healthy beyond this point. To create a new culture, just replicate everything listed above, and transfer some of your existing microworms to your new culture.

Most cultures will do well at room temperature, and seem to do better in a well lit room. Never let a culture fall below 32 degrees, and they should be kept somewhere between 70-85ºF (21-29ºC)  optimally. I’d also like to stress that you should always keep multiple cultures going, since crashes while rare, are not unheard of. And if you’re culture crashes and you only have the one, then you’ll have to track down another starter culture.