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Culturing Redworms for Tropical Fish Food

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Most aquarists are perfectly happy with using commercially prepared dried foods or commercially prepared frozen foods. However, some of us either want to be cheap, are hungry for more challenge, or perhaps want to have a more self-managed food supply. Here I will be telling my method of culturing redworms for use as fish food. I am by no means an expert, but here is what I have learned in the past couple of months, coupled with some common worm knowledge. This is not meant to be a sole resource, there is much more information on composting with worms (vermicomposting) on the internet and in a few books. Done correctly, by the time this project is up and running you should be able to harvest worms regularly for your group of fish.

Setting it up:

Redworm Culture Setup  You will need:
  • A large container*
  • Bedding material**
  • Paper cardboard or similar
  • A three-pronged cultivator or similar tool
  • An initial supply of worms
  • Worm food supply
  • Something to cover the bin
  • A tray for the bottom of your container (optional)
  • A cool place outdoors or in the garage
  • * Preferably with drainage holes at the bottom. I used an old recycling bin...you could also make one using wood.
    ** Coconut coir works well, but you can also use fertilizer free potting mix.

    Get your container. If it doesn't have drainage holes in the bottom it would be a good idea to make some. It would also be a good idea to have a tray on the bottom, so that whatever is under your worm bin does not get soiled. Worms will not venture from inside the bin if the conditions are favorable.

    Now, get your bedding. If you decided to use coconut coir you probably bought coconut coir bricks. Soak in water according to the instructions and then put them in the bin. Do not pack down or anything, as you will need to mix more in later. You could get enough bedding to fill the whole bin, but that is not necessary...paper and cardboard will add a lot of bulk.

    Next, get your paper/cardboard. If you want you can shred the paper so it mixes easily into the bedding, but this is not necessary. Same for the newspaper. Unless you are insane you will not try shredding cardboard now.

    Now, soak your paper and cardboard underwater for at least a day. A pond or even an extra sink or bathtub works well for this. Be sure none of the others sharing the house mind. After the soak, the paper and cardboard should be very soft. If you haven't shredded your paper, perhaps try doing it now by hand. Should be very easy to turn into strips. The cardboard will probably be easy to peel into paperlike sheets. If you did like me and used a pond, you could leave the paper/cardboard long enough that it begins to decompose slightly, which will make it even softer.

    Mix your paper and cardboard in with the bedding in the bin...trying to get it mixed in as evenly as possible. If the bedding has dried out, add enough water to it to soak it thoroughly. Take your cardboard sheets, cut into a few pieces, and lay on top of the bedding. This will conserve moisture and also keep the worms close to the surface. I put a whole piece of cardboard on top of this, but this didn't seem necessary.

    Leave this to dry for some time. It is now ready for adding worms. Redworms (Eisenia foetida) can be bought in bulk (by weight) online. Overall, these are probably the best worms to be raised for feed fishing. The European Nightcrawler (Eisenia hortensis) is sometimes used because it grows larger. However, it reproduces slower than the redworm. Some people use both. Buying these worms online is much cheaper than buying them in cups from the bait or pet store. However, one pound (the usual minimum amount in the USA) is a considerable number of worms. If you don't need lots of worms at first, you could simply start with a few cups of worms and wait for the population to build up. Put the worms and whatever bedding they came in on the surface. Keep the area well lit to encourage the worms to burrow into the bedding.

    Lastly, you need a cover for your bin. A piece of wood works well and if your container happened to come with a secure lid that is even better. The cover should be able to keep the worm bin dark and also hold moisture in, so you will not have to water the bin as frequently.

    Maintaining the worm bin

    Thriving Redworm Culture After introducing the worms, leave them for about a day or so. You can then offer small amounts of food. Pretty much anything that is thrown into the worm bin will disappear. I'd recommend starting with something such as a few fish pellets or a sprinkle of cornmeal, before eventually adding more things. Some items which I've added to the worm bin have been fish food, cereal, tea bags, apple and pear cores, cantaloupe with skin, strawberry tops, lettuce, banana peels...almost anything goes. It is said that worms will not take citrus due to the amount of acid it has. Although it should be obvious, do not put meat, manure, or anything that will take an extremely long time to decompose into the bin. Using some common sense when adding food should keep you safe. Do not add too much at one time and do not add food always in the same spot. Also, what is very important is to bury the food at least a few cm under the bedding. This way you are not as likely to attract other bugs such as fruit flies to the worm bin. Depending on the size of the worm bin the worms will eventually be able to process large amounts of food, but increase the amount gradually.

    The worms prefer temperatures that an average human would be comfortable at. It is best not to expose them to extreme temperatures. Any changes must be done gradually as with fish. Also, although the bin must be kept moist, it should not be allowed to dry out or to become too wet. About the moisture of garden soil would be good. Keep in mind that the bottom of the bin will be much wetter than the top. While it might look relatively dry at the surface the bottom could be sopping wet. While this is not much to worry about, if too much water is added the consequent anaerobic conditions will kill the worms. If conditions are good the worms will reproduce rapidly. The worms will lay small red egg cases that are easy to see in the bedding.

    The worms not only eat up the food, but also the bedding you added will eventually get processed and turned into waste matter (gardeners refer to it as worm castings). So eventually you will have to replace the bedding. The bedding will turn darker as the worms eat it and replace it with waste material, and it will also compact. People generally change the bedding between once every six months and once a year. People have thought up many ways of removing the bedding without removing the worms. The simplest method is to add food only on one side of the container. After a few weeks (providing the bedding has been mostly eaten up) almost all the worms will have congregated on the side where you put the food. Then it is a simple matter to remove half the bedding and replace it with new. If you want to make sure you don't throw out any worms you could leave the old bedding in a pile where it will slowly dry. Remove the outer layers as it dries. Whatever worms still in the bedding will eventually have congregated in the center and can then be collected. While we are concerned about getting worms to feed our fish, most people raise red wigglers because the resulting "waste matter" in the form of worm castings makes excellent "fertilizer" for the plants.

    The bin often gets other visiting creatures besides the worms themselves. Besides the billions of invisible protozoans that help break down the bedding and provide food for the worms, there are also creatures that are visible to the naked eye. Perhaps the most common would be springtails. These small (1-4 mm) insects almost always are present in the worm bin. They are easily distinguishable by the fact that they can jump using a small catapult like structure folded under the body (thus the name springtail). They are harmless to the worms. Fungus gnats are small black flies which may be seen flying feebly over the compost. Once again these are harmless but may be an annoyance inside the house. If you do not bury your food well enough or add too much, fruit flies may find your worm bin. Mites are another indicator of too much food. They are almost always present, but if too much food is offered they will multiply to amazing numbers. Another similar "pest" would be whiteworms. They seem to find just about any bin sooner or later and populate it. Of course, for us fishkeepers this simply means yet another source of food! If you take proper measures to bury the food and don't feed too much at one time, these should not be a problem. Another problem that may happen feeding certain kinds of food is that the bedding will go acidic. This can be corrected using limestone (calcium carbonate) to raise the pH. It can also happen if you start with a bedding that is too acidic (which is why coir should be preferred over peat).

    Feeding Redworms to Fish

    You may be wondering what kind of fish would like redworms. The best answer would be: almost all of them! Redworms work best for fish that eat lots of meaty foods or insects in the wild. Many cichlids, carnivores and (in my case) killifish will enjoy redworms. Keep in mind that redworms are a rich food, so if the fish in question is one that you would not feel comfortable feeding lots of blackworms or bloodworms to you should take caution with redworms. In any case you should be sure the worms are appropriately sized or well chopped. Too much or unchopped worms is said by some fishkeepers to cause bloat.

    Harvesting and preparing the worms is a simple matter. Depending on what kind of fish you have you may offer the worms whole or chopped. Keep in mind that, if crowded, the worms will naturally be smaller. Simply lift the pieces of cardboard you put on the top and collect any worms under them. If no worms are under the cardboard then you can use a tool (preferably something like a 3 pronged cultivator so you do not cut apart the worms when you dig) to go down a few cm to collect the worms. The worms will often congregate around the area where you added food last. Before feeding the worms, it is best to squeeze out the "dirt" in the worm by running your fingers along its length...head to tail. Feed them to the fish whole or chopped. Keep in mind that smaller pieces are easier to digest so, if in doubt, chop the worms well. It is quite simple to place the worm on a flat surface and using scissors, a razor, or anything else handy to slice the worm into appropriate sized pieces. For certain fish you may want to keep the pieces long enough that they can wriggle and attract the fish's attention.

    That's about it! Once again, this isn't meant to be your only source, so please do further research for additional information concerning growing redworms, so you can better "personalize" whatever setup you choose to make. While this is likely unnecessary if you only have a few fish that like worms as an occasional treat, if you are dealing with something which you must feed a good amount of these, or perhaps a large number of fish, this would likely be less costly in the long run. You also get the satisfaction of knowing you raised them yourself!

    Joseph (nonamethefish)
    Read other fishkeeping articles by this author in his personal website
    Reader Comments Comment

    Interesting to note that the above recipe is typically used for indoor composting. I am a gardener in NYC, where outdoor gardening, much less outdoor composting, is not something everyone can do. Though I personally bring my organic waste to job sites where I can turn them into compost, it is good to know that one could do indoor composting as well as feed the fish with the worm supply that multiplies rapidly. What an excellent way to recycle and be green. Bravo!

    Contributed by Ilya

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