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Microworms - which are actually nematodes, not worms - are a convenient live food because cultures can be maintained almost indefinitely with very little maintenance.

Microworms - which are actually nematodes, not worms - are a convenient live food because cultures can be maintained almost indefinitely with very little maintenance.  Unlike live brine shrimp, microworms don't have to be hatched and then immediately fed to your fish. An individual culture will last 4-6 weeks, with live worms being harvested and fed every day.

Microworms are a good food for fry that are too small to consume baby brine shrimp or dry foods. In my fish room I feed them to Melanotaenia Praecox (dwarf neon rainbowfish) fry because their mouths are not big enough to eat baby brine shrimp for their first 1-2 weeks. 

I shot the video below using a small microscope to show microworms moving in water. The larger hash marks are 1 mm apart, the largest microworms are about 1 mm in length, however they are only about 0.1 mm wide. This allows very small fish to slurp them up like noodles. You can also see much smaller worms that are only 0.2 - 0.3 mm long. The round objects are pieces of potato flake from the culture.

microworms under a microscope

How to Start a Microworm Culture

The first step to starting your own mircoworm farm is to obtain a starter culture. These can be found for sale on eBay, Amazon.com, or through local fish shops and aquarium clubs. A starter culture will be relatively inexpensive (usually around $10 for a good culture) and the best part is you will only have to pay this one time. Some people out there are selling cultures for as low as $3-$4*, but I strongly recommend paying slightly more for a culture that comes with worms, yeast, a container, and some instructions to get you started.

*I tried buying a culture for less than $4, and when it arrived it was a tiny bag in a standard letter envelope containing about a teaspoon of worms that smelled like death. It was a waste of money & time.

Once you have a starter culture and you begin setting up your own cultures, you should be able to keep live microworms available for your fish for as long as you want. The video below by Aquarium Co-op has a lot of good information on how and why you should set up a microworm culture.

Selecting a Container for your Microworm Culture

You can use just about any plastic container for a microworm culture, as long as it has a lid and a flat bottom to spread the culture media on. I like to use plastic containers from salad mix or packaged lunch meat that have been washed out.

Microworm Cultures
Microworm Cultures

Nematodes need oxygen to live. I use a utility knife to cut small air holes in the lid of the container. These holes don't need to be very big, just enough to allow some air to reach the culture. 

Utility Knife
Utility Knife

Selecting a Medium for your Microworm Culture

I use an instant potato mix as the base for my microworm cultures, as recommended by Aquarium Co-op. Other options include oatmeal, cornmeal, and baby cereal. Any of these soft grain mixes will work, but I've found the potato mix to be very cheap and easy to use. Just make sure whatever you buy has no additives.

Potato Mix
Potato Mix

Starting a Microworm Culture

Once you have starter worms, a container, potatoes, and some bakers yeast, you can mix up a new culture.

  1. Pour enough mashed potato mix into the container to cover the bottom with about a half inch layer. This will expand when water is added.
  2. Add water from an aquarium and stir until the mixture is similar to mashed potatoes. You don't want it too runny or too dry, it should look like the photo on the box.
  3. Smooth out the mixture in the container
  4. Add a little bit of baker's yeast, and gently stir it into the top layer of the mix
  5. Smooth out the mixture and add two spoonfuls of aquarium water to wet the top
  6. Add the worms from your starter culture to the top of the mix, put the lid on the container (make sure you date it!) and wait a few days (3-5 days on average)
  7. Once you can see the top of the mixture shimmering or wiggling, you know the worms are multiplying. They can now be harvested using your finger or a spoon, paintbrush, etc. Just dunk them into the aquarium!
New Microworm Culture
New Microworm Culture

Keeping Your Microworms Going

To make sure you never run out of microworms, its a good idea to always have 2 active cultures. I start a new culture every 3-4 weeks. Make sure you write the date you started the culture on the container!

Your existing cultures should be stirred gently about once a week to keep them thriving. They will have a vinegar-like smell to them, which is normal. If you can see live worms and don't see any mold, it is probably still good. Eventually the culture will start to stink badly or grow mold, and it should be discarded. This will happen after several weeks.


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Why Feed Live Baby Brine Shrimp?

Fish thrive when fed live foods often, especially when they are young. Live baby brine shrimp are a highly nutritious food for fish fry; full of protein and nutrients that dry flake food just doesn't offer. Newly hatched brine shrimp are very small, measuring less than 1 mm. Fish of most species are able to eat them within their first week of life. Additionally, fish love brine shrimp. Almost any fish will eat them live or frozen.

The photo below shows a newly hatched and strained batch of baby brine shrimp.

Baby Brine Shrimp in Coffee Filter
Baby Brine Shrimp in Coffee Filter

Hatching Brine Shrimp

Brine shrimp eggs are actually dormant cysts. They can stay viable for years if they are stored in a cool, dry container. When exposed to warm salty water, they re-hydrate and begin to hatch. Hatching baby brine shrimp is pretty simple. Below is a list of the materials you'll need to start your own hatchery.

1. Container

The optimal container for hatching brine shrimp has a tapered or conical shape. A very cheap and reliable option is to use an inverted plastic soda bottle. A 1 Liter bottle will work for small batches but a 2 Liter is more efficient. The photo below shows a 1 liter water bottle being used to hatch brine shrimp.

1L bottle brine shrimp hatchery
1L bottle brine shrimp hatchery

Another option is to purchase a specially designed brine shrimp hatchery like this one. This may be a good option if you want something sturdy that can be used for a long time.

2. Aquarium Salt

Brine shrimp, as the name implies, require a brine solution to hatch. The typical solution is about 1.5 tablespoons of salt per quart of water, or 25 parts per thousand of salt. Although you don't have to use aquarium salt, I like to use it because the large crystals are easier to work with without making a big mess. A large container is not very expensive, and will last a long time if you are just using it for this purpose.

Aquarium Salt
Aquarium Salt

3. Air

Hatching brine shrimp requires an air pump to tumble the cysts in the water and keep the solution oxygenated. You don't need an air stone. Just position the airline tubing so that the bubbles are coming out at the very bottom of the container.

4. Brine Shrimp Eggs (Cysts)

There are several different brands of brine shrimp eggs available. For the most part any brand that advertises a high hatch rate (80-90%) will work. The San Francisco Bay brand is popular and a good choice if you are just trying to hatch them for the first time. However, its more economical to buy a large container, like this one.

Brine Shrimp Eggs
Brine Shrimp Eggs

Hatching

Once you have all the materials, you can set up your hatchery and mix up the water, salt, and brine shrimp cysts. There are many different DIY brine shrimp hatchery designs out there. This one by Solid Gold Aquatics is a good beginner tutorial.

In my experience you don't need to add anything to the water besides salt. This includes dechlorinator. The cysts are completely encapsulated and chlorine in normal tap water concentrations shouldn't affect your hatch rate.

The optimal temperature for hatching is 77-80F. Since brine shrimp are attracted to light sources, you can use a lamp with a CFL or incandescent bulb to keep the solution warm, or submerge the bottle in an aquarium that is already at a nice warm temperature. I have found that temperature is more important than constant light for high hatch rates.

Hatched Baby Brine Ready to Harvest
Hatched Baby Brine Ready to Harvest

Harvesting Brine Shrimp

When you are ready to harvest your newly hatched brine shrimp, you should remove the air line and allow the solution to settle for 5-10 minutes. The unhatched cysts will sink to the bottom of the container, and the empty shells will float to the surface. This will leave the live baby brine shrimp swimming in the middle of the solution. Then use a pipette or turkey baster to suck up the wriggling orange cloud.

At this point you can squirt the salty brine shrimp solution directly into your aquarium, but it is better to strain the shrimp out of the salt water using a coffee filter first. You can use either a fine metal mesh or a paper filter for this purpose.

Straining Brine Shrimp
Straining Brine Shrimp

Once you have strained the shrimp into a filter, you can transfer them to some dechlorinated tap water or aged aquarium water before feeding them to your fish. Any leftover baby brine shrimp can be frozen into cubes and fed over the next few days.

Using a Pipette to Suck up Baby Brine
Using a Pipette to Suck up Baby Brine Shrimp

The video below shows live baby brine shrimp being fed to my celestial pearl danio tank. You can see just how quickly the fish devour them.