Walter Worms as Live Fish Food: The Ultimate Guide


What are Walter Worms?

Walter Worms (Panagrellus Silusioides) are a species of nematode which is commonly grown as live fish food, especially for fish fry and juvenile fish. They are clear to white and have worm like shape and movement. This species is very small and can be hard to see without a magnifying glass or stereo microscope. Walter Worms aren’t parasitic and are completely harmless to humans. They are a fairly new discovery, only being classified in 2002 by Helmut Walter. Walter Worms are a great first food for tiny fish fry which may have trouble eating larger live food such as brine shrimp.

Use of Walter Worms as Live Fish Food

Walter Worms are a great choice for feeding tiny fish fry. Brine shrimp are often used as fry food but they can be larger than some tiny fish fry can eat. Betta fry are very small and Walter Worms are one of the first foods they can eat. While they are a popular food with Betta breaders they can also be used with other small fish fry like Guppies, Angelfish, Killifish, Barbs, Danios and Neon Tetras. Many tiny fish fry can benefit from small live foods like Walter Worms. Depending on the fish you are breeding, other fry foods can be an option as well. It’s a good idea to have multiple cultures of Walter Worms growing in case one or more fails. You should feed your fry more than just Walter Worms if possible. A varied diet is the best choice if you want healthy baby fish!

Walter Worms (Panagrellus Silusioides)

How to Culture Walter Worms

Walter Worms can be cultured very easily, but there are a few things to keep in mind. Here are some steps on how to culture Walter Worms.

1. Assembling your Walter Worm growing equipment

Before you start cultivating Walter Worms you’ll need to put together some equipment. You’ll need Walter Worm starter culture, plain instant mashed potatoes, a few small plastic containers with tall sides and good lids. You’ll also need un-chlorinated water. This can be bottled water, RODI or distilled. You won’t need to get more Walter Worm starter culture each time you prepare a new growing container: your spent Walter Worm batches will have enough live worms to start a fresh culture. Your first batch of starter culture will probably come from on-line sources or from a local fish store. Starter culture won’t last forever, so when you receive your culture it’s important to start your growing container soon while it’s still fresh as possible. Also be sure the instant mashed potatoes you use are plain and don’t have any extra flavorings or additives. Read labels carefully to verify that they only contain potatoes and don’t have added salt or flavor.

2. Prep your Walter Worm growing containers

Your Walter Worm culture will need to breathe so you want holes in your container’s lids, but these holes will need to be covered. This will prevent the worms from crawling out and keeps other insects from getting in and infesting your culture. The best way to do this is by cutting openings in the lids and taping a piece of coffee filter or some filter floss over this hole. Make sure it is covered with tape on all sides and only the top of the filter material is open to air. It’s also a good idea to write dates on your containers so you know when you started each culture and what type of worm is growing in each one. You’ll likely have different cultures growing at different start dates and may branch out into other types of microworms, keeping track of which container contains what will be important as they grow and mature.

3. Growing Walter Worms

When you are ready to start a new culture, place a half-inch layer of instant mashed potatoes inside a container. Add bottled, RODI or other un-chlorinated water and mix. You need enough water to give your mashed potatoes a fluffy mashed potato texture but not so much that they turn into a soup. Some growers will add instant yeast to their mashed potato growing media but this is probably unnecessary. Next, spread your Walter Worm starter culture over the top of this mix and seal with one of the lids you prepared earlier. This container should be stored somewhere out of direct sunlight but where it can stay warm. As long as your culture doesn’t get too hot you can store them wherever it’s convenient. Split your Walter Worm starter culture between a few different batches just in case: it’s possible for a particular batch to spoil and you’ll want some backup cultures running if this happens. Keep an eye on your cultures and be ready to discard any that start to get moldy or become infested with unwanted insects. You only want to feed your fish fry with Walter Worm cultures that are healthy and have been growing well. If a culture is spoiling it is safer to throw it out rather than risk feeding your valuable fish fry impure food.

4. Harvesting Walter Worms to feed fish fry

Keep an eye on your Walter Worm cultures and watch for signs of life. You should eventually see the tiny worms crawling up the inside walls of the containers. Harvesting these worms is easy: just remove the lid and wipe along the sides with a cotton swab or a clean finger. Rinse the worms directly into your fish fry’s tank. Don’t overfeed your fish fry as Walter Worms will only live 12 or fewer hours in water. If you overfeed, the dead worms can spoil the water in your fry tank. These cultures will continue to grow and produce more worms for a few days. Eventually the worm’s waste will build up and then it’s time to discard the culture and start a new one. Remember that you can use older healthy cultures, even those which aren’t producing many worms, to start fresh batches.

5. Starting more Walter Worm cultures

There is usually no need to buy more Walter Worm starter culture once you have a few batches going. Even spent batches that aren’t producing many worms can be use to start fresh colonies. You’ll need to make sure that you only take worms from healthy cultures that aren’t moldy or spoiled. Prepare fresh culture containers with media, but instead of starter culture use a smear from the walls of one of your older batches. Try and avoid bringing in the mashed potato mixture from an old culture: it is best to only harvest the worms from the container’s sides without cross contaminating your new growing media with the mashed potato mix from an old batch. Batches can fail so it’s always a good idea to create more batches than you think you’ll need as a precaution against any particular batch failing. This way you can be sure you’ll have enough Walter Worms ready when you need to feed your fish fry.

Where to find Live Walter Worms for sale

You can get Walter Worm cultures from on-line sources or from many local fish stores. If you know other fish breeders in your area you may even be able to get some starter from them. Walter Worm starter cultures are more expensive than some other types of microworms commonly used for fry food. Prices are not prohibitive and you should expect to pay less than $10 USD for starter culture. It is difficult to collect Walter Worms in the wild and most people use starter cultures to ensure they have the correct type of worm. It is unlikely that you’d be able to collect Walter Worms from soil. There are lots of different small worms that live in soil and probably many which you wouldn’t want to feed to your fish fry. Always use Walter Worm cultures from reputable sources to make sure your colonies have a pure and healthy start.

Walter Worms vs Microworms

Walter Worms are smaller than Microworms (Panagrellus redivivus), which are another type of small worm which is commonly used for fry food. They are both good choices when feeding very small fish fry which might have trouble with larger foods. Microworms (Panagrellus redivivus) are very similar to Walter Worms, and can be cultivated with the same method. Walter Worms and Microworms (Panagrellus redivivus) both have a similar nutritional profile so it really comes down to your personal preference. Microworms are very popular as fry food and it may be easier to find starter cultures for these worms. Walter Worms are a bit rarer and starter cultures tend to be more expensive. Once you have healthy batches of either worm it’s easy to start more cultures so initial cost is less of an issue.

Walter Worms vs Vinegar Eels

While both Walter Worms and Vinegar Eels are used to feed tiny fish fry they are grown using different methods. Vinegar eels grow in a mix of unfiltered apple cider vinegar, water, and apple slices. Vinegar eels are a bit harder to harvest and need extra steps which involve packing filter floss into the neck of their growing container and filling with pure water, after which the Vinegar Eels can be pulled out with a pipette. Walter Worms can be simply wiped off the sides of their growing containers and directly added to tank water. Some fish breeders feel that vinegar eels are a healthier food for fry and will go to the extra trouble of raising them.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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