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Baby Brine Shrimp and Microworms

by TFH Magazine on November 2, 2010 at 6:08 am

By Mike Hellweg
I feed newly hatched brine shrimp (Artemia nauplii) to my fish every day, and have done so for more than 30 years. It is one of my keys to success in raising large numbers of fry. During this contest, I have had to increase my production considerably. I’ve moved from using two 2-liter hatchers to using 3-liter ones. I’ve increased the production per hatcher from one teaspoon to one half tablespoon per day per hatcher—more than double the production. Instead of going through a one-pound can every 48 days or so, I’ve been going through one every three weeks! One thing I would like to note here is that during the year, several of us in my local aquarium club made the mistake of buying from one supplier that only puts 14 oz in a “one pound” can for about the same price as others sell a full pound – that was really noticeable. Lesson learned – always check to make sure it is a full pound that you are paying for!

My hatch procedure is exactly the same as I’ve used for decades—it’s simple and it works. Like many of you, I like to experiment and I’ve tried other “better mixtures” and always have found that my simple procedure works best for me. Some people like to go through the extra step of decapsulating, but I’ve found that an unnecessary step. They argue that the nauplii use up a lot of energy in hatching. It is true that the nauplii do use up some energy, but it is such a small amount that a single fry need only eat one more nauplius to more than make up the difference. Since they’re each eating dozens to hundreds per feeding, one more nauplius or one less doesn’t really make a lot of difference in the overall scheme of things, negating this argument. So in my opinion it’s whether or not you want to go the extra step. I just don’t think the extra effort is worth it for the miniscule payback. What is important is to feed the newly hatched shrimp to your fish as soon after hatching as possible. Never let your hatched shrimp sit for more than 5 or 6 hours post hatch. I set mine up to harvest at the 24 hour point. This makes sure almost all of the eggs that are going to hatch have had time to hatch, and even the earliest ones to hatch haven’t been out of the shell for more than a few hours.

Nauplii in a catch cup ready to feed

Nauplii in a catch cup ready to feed brine shrimp

In a 2-liter brine shrimp hatcher add two tablespoons of plain table salt (iodized or not—it makes no difference—growing fish need iodide in their diet just like humans do, and contrary to internet rumor passed along as “fact,” the miniscule amount that would get into the aquarium with the brine shrimp is harmless), a tablespoon of plain Epsom salts, and up to a half tablespoon of eggs. Add plain cool chlorinated tap water, no need to dechlorinate. Then add one to three drops of plain bleach. Cover the container and add aeration – just enough to keep everything swirling in suspension. Let it run for 24 hours at 78° to 80°F. No more. Turn off the aeration and let it settle for 15 minutes. I use a small nightlight next to the hatcher to attract the nauplii to one point in the container to make harvest easier.

I run a siphon from the hatcher to a plankton sieve in the sink (a permanent coffee filter would work just as well). The hatch water goes down the drain. I never reuse it. Reusing the hatch water is a false economy. Sniff it. Would you feed that to your fish? Why try to grow food in that stinky mess? It is full of bacteria which compete with the newly hatched nauplii for oxygen. It is also full of waste products from decaying dead shrimp, and, if nothing else, it takes several extra minutes to clean out the unhatched (or dead) eggs and hatched egg shells. By the time you do this, you could have rinsed out the old container and re-set it with new water. Cost of salt and Epsom salts is negligible. Over the course of a year, it runs to less than $10 for all of the eggs I’m hatching. Why reuse it?

I then rinse the nauplii under a slow flow of cold tap water and rinse them into a catch cup (the kind shops use when they catch your fish). I can hook this on the tanks as I move around the fishroom and feed the fish. I feed with a small turkey baster. That’s all there is to it!

I also feed a lot of microworms. The ones I’m using during the contest are known locally as “banana worms”. There are also microworms, mikroworms, Walter worms, potato worms, and likely others as well. All are small nematodes less than an eighth inch or so at maturity. I believe all are livebearers, but I’m not 100 percent sure about that. All are cultured in the same way. I’ve tried a lot of the methods for culturing them (over 40 different methods when I wrote my first book a few years ago) and found this to be simple, reliable, and able to produce all of the worms I’ll ever need. Others argue their chosen medium is best. They’re right. Whatever works best for you is what you should use.

I use quart sized containers with a 6 x 3 inch bottom and 2 inch high sides. They come with sandwich meat from the deli. I add enough mixed baby cereal to cover the bottom to a quarter inch in depth and mix in a quarter teaspoon or so of yeast. I then add enough dechlorinated water to make the whole mix mushy but not quite wet, and add a starter culture of banana worms. I cover it with the lid that comes with it and put it in my live food cabinet in my fishroom. I poke about 100 pin holes in the cover. This allows oxygen exchange without allowing other critters into the culture. Within five or six days the sides are covered with worms and the culture is ready to harvest. I swipe my finger around the sides and remove all of the worms that I can. I then rinse this into a catch cup. I dip my finger into the medium of the culture a couple of times and add this to the catch cup as well. It is now ready to feed my fish. I feed with a small turkey baster, just as with my brine shrimp.

Differences in the various Nematodes:
Microworms and Mikroworms (This is a trade name and may represent a different, closely related species. They are sold desiccated and must have water added to reactivate them and get them going.) They reproduce relatively slowly and are just a bit larger, relatively speaking. They are also a bit more slender. They sink quickly in the water column and are great for young catfish, cichlids, tetras, cyprinids, and Anabantoids that spend their time near the bottom.
Banana worms reproduce extremely quickly and will get production up quickly if you need a lot of nematodes fast. They also seem to sink pretty quickly and are great foods for all of the above fish fry.
Walter worms are a bit thicker and just a bit shorter than microworms. This makes them sink quite a bit more slowly in the water column and makes them great food for surface and mid water feeders like many killies and livebearers. They will also reach the bottom and can be used for all of the same fish as microworms.
Potato worms may or may not be another nematode species. They are cultured on potato flakes. I’ve never cultured them or used them as food so I cannot comment on their culture method or distribution method in the water column.

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Posted in Breeder's Challenge by TFH Magazine on November 2nd, 2010 at 6:08 am.

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