OK, the scientific stuff can be found on Wikipedia however what you really need to know is that they are a great source of food for your fry and even full grown Guppies. My Cherry Red Shrimps also spring to life trying to catch a feed of Micro-Worms.
They are not quite microscopic worm like (not actually worms funnily enough) organisms that feed primarily on yeast. They mature very quickly (about 3 days) and reproduce with live offspring... this means you have a great and constant supply of live food for your fry.
Unlike Baby Brine Shrimp which is another good live food for fry there is a lower risk of your fish or fry "choking" on an unhatched cyst.
They are really easy to keep although can get a little smelly. Can be cultivated on a substrate of oats and a sprinkle of dry yeast. No special equipment, not much effort, not too much money to spend. A really good option.
You can easily find culture by doing a search on ebay, your local fish forum or trying your local aquarium supply store or pet shop. They are usually not readily available in aquariums or pets shops (in Victoria anyway). Of course you can support my efforts by buying them from the Guppy Club store or the quick link button at the top of this page.
This is so easy a child could do it in fact even I can do it!
For a container a washed and well rinsed take away food container is fine. Use a 'Hot Nail" or small soldering iron to make a series of holes in the container lid. I make about 6 holes.
I've read and seen others put cotton wool into these holes, this is supposedly to prevent unwanted critters getting into your culture. Personally I don't bother and have never had a problem. (fingers crossed)
The holes help let out the humidity that builds up in the container and provide a small amount of air flow.
Then simply put 1/2 cup of quick oats into your container (less or more depending on the container size). Add just enough water to moisten the oats without making the mixture too wet. The consistency is difficult to describe... a rough paste maybe. Flatten out with the back of a spoon.
Sprinkle about 1/4 teaspoon of dry yeast over the top of the oats... done!
Starting the culture is as simple as transferring some of the micro-worms across to the new substrate. I find the easiest way of doing that is to dip your finger into some fresh water and swiping the side of the container of the starter culture then gently dabbing the new substrate.
In an established culture you will find that a pool of white "milk" forms in various places. Filling a pipette with fresh water squirt this into the milk and agitate the container then tip to one corner and again use the pipette to transfer the "milk" simply put a small amount in several places across the culture. Within a week you should see the micro-worms migrating up the sides and onto the lid of the container.
Store the culture at room temperature. I have about 6 cultures all a week to 10 days apart. Typically I use the oldest culture first when that starts to "die off" I make another one and put the first in the compost heap. The cultures do seem to accelerate at one point and then as the food source runs out it starts to slow down and eventually dies off.
To feed the culture to your fish and fry is easy. I dip a finger into the tank then wipe the wet finger across the side of the micro-worm container to collect the micro-worms then simply rinse the finger back into the tank. You can use a cotton wool bud or small paint brush for this if you don't like or want to use your finger. I haven't been eaten alive myself and use my finger so it seems quite safe to do so.
That's about it.
Micro Worms are high in Fat. This is a good thing in moderation. Ideally Micro Worms should not be the sole source of food for fry. Combined with Baby Brine Shrimp or another commercial fry flake/powder they are the perfect supplement.
Fry fatten up fast and have plenty of energy. I like to provide a strong current in my fry tanks to encourage strong vibrant fish the high fat diet is then used as a source of energy.
Besides the initial outlay for a starter culture keeping Micro Worms must be one of the most inexpensive live foods available. If you consider the starter culture, some containers, and some oats you can harvest a years worth of food for 10000 or more fry for under $15.00 - now that's the cost of about 3 cups of coffee and let's face it fry don't even like coffee!
Instinctively fry love live food. The movement of the food triggers a reactive frenzy and the fry generally gorge themselves. This promotes fast growth and good health. Remember though only feed as much as the fry can eat within 10 minutes and clean up any excess. Like any left over food it can quickly foul the water and create an unhealthy environment that promotes disease and stress on your fish.
This picture was scraped off the net but is a good picture of a healthy Micro Worm Culture in Oats. Full credit to the photographer and owner of this pic.
Our starter cultures are provided in a closed small tub with pin holes in the lid. This is then put in a ziplock bag and posted. Typically they arrive in good nic ready for you to start your own cultures.
We grow our culture in "quick" oats with a sprinkle of dry yeast. This base reduces the smell, is clean and safe for your fish and tank.
A full set of instructions is included for your convenience.
Micro Worms are just visible to the naked eye when put in water. About 1.5 - 2mm long and a fraction of a mm round.
Very high in fat and good source of protein. Micro Worms are a good staple food source for adults and fry.
15 Minutes once a fortnight will maintain enough Micro Worms for the average guppy keeper.
Micro Worms don't really fowl the water. They stay alive for 24 hours or more settling on the bottom of the tank. Like any food left overs should be removed, better still don't over feed.
Micro Worms are simple to use. Dip finger in tank, swipe side of culture container, dip finger in tank; Done!
Of course you can use a cotton wool tip if you are screamish :-)
Micro Worms (still alive) settle en mass. I've seen my fry "belly scuff" the Micro Worms on the bare tank floor to agitate the worms back into the water for ease of eating.
Fact: Micro Worms are not worms rather
Micro Worms can omit a foul odour. They can get infested with mold. Can "crash" and you'll need to acquire more culture. They can escape too but they don't get far.