Text Box: BLOODWORMS by steve hopkins


by steve hopkins

reprinted from:

Koi Talk, Newsletter of the Hawaii Goldfish and Carp Association

January, 2007


Bloodworms are the larvae of the midge fly.  A midge fly is about the same size as, and looks sort of like, a mosquito.  But, they do not bite.  If you see a mosquito-like thing with fluffy antenna and no proboscis, it is probably a midge fly. 


Midge flies lay eggs in water.  The eggs mass is a small clear jelly-like glob that looks much like aquatic snail eggs.  The eggs hatch into small worm-like larvae.  If you look at the larvae with a magnifying glass or microscope, it appears less worm-like and has a segmented outer shell like other insect larvae.  Midge larvae have a bright red color.  The red coloration is from a hemoglobin-like substance which allows them to live in water with very little oxygen.  Thus, midge larvae are red for much the same reason that our blood is red – because it carries oxygen.  It is then not too surprising that midge larvae are called blood worms.


Bloodworms spend most of their time attached to the bottom or other solid surface.  Older and larger bloodworms may get up and move around some at night, but for the most part they sit still and grab bits of stuff to eat as it floats by.  To attach themselves to a surface and help protect themselves from predators, bloodworms make a tube to live in.  The tube is made out of bits of mud, mulm, algae or whatever is available.  They sort of stick it together with spit and build a tube around them.  You have probably seem these tubes but did not take much notice.  They are about a half-inch long and either straight or crescent shaped.  Set a pan of water outside and add a little fine soil or finely-ground meal.  Within a few days you will see bloodworm tubes appear on the bottom and sides.


What do bloodworms have to do with goldfish and koi?  Well, there may be no better food for our finned friends than bloodworms.  Put a goldfish or small koi in that pan of water and the bloodworm tubes will disappear in no time.  For large koi, bloodworms are a little small to make a meal out of, but they will eat every one they find nonetheless.  It does not take too many bloodworms to fill up a goldfish.


Frozen bloodworms can be purchased at better pet stores.  There are small cubes in a 3.5 oz. blister pack.  Cubes can easily be popped out of the frozen package and put directly in the tank or pond.  The frozen cube thaws and the individual worms float free in a few seconds.  The cubes cost about $15 per pound.  Bloodworms are also available in bulk one-pound packages which cost about half as much per pound.  For the bulk packs, a chunk is broken off and thawed.  It’s a little messy, but less expensive. They are also available as a freeze-dried product but the fresh frozen form is thought by many to be better. 


We can easily grow and collect bloodworms at home.  As noted, all it takes is a container of water with some sort of sediment for them to eat and make tubes out of.  For sediment, you can use crushed fish food flakes, rabbit food (the pellets dissolve and fall apart), bakers yeast, flour or green water (water full of single cell algae).  The small worm tubes appear in just a few days and they are full size in a little over a week.  To collect them, just brush the sides and bottom of the container to dislodge the tubes and collect them in a fine-mesh net.  The mesh opening of the net should be less than 1/32-inch (about 500 microns) to keep the smaller worms from going through.  If the netting size is correct, he tube material can be washed through while the worm is retained.  However, you may want to consider giving the fish the whole tube with the bloodworm inside.  They will eat it all.  Bloodworms grown in green water are encased in a tube which is largely composed of algae cells.  Eating algae helps goldfish avoid swim bladder problems.


How many bloodworms can you grow?  Well, it is reasonable to expect to get about 100 per square foot per week.  A dish pan can make enough for a nutritious meal for goldfish tank each week.  What would it cost to buy that same quantity of worms in the pet store?  About a penny.


Why would we bother to buy frozen bloodworms, much less take the time to grow them ourselves?  As noted, bloodworms are great nutrition for goldfish and other carp.  For goldfish with a head growth (wen) like oranda and ranchu, bloodworms and other natural foods are thought to be particularly important.  Many serious goldfish keepers think that good head growth development is impossible without feeding bloodworms. 


Why or how do bloodworms work so well?  No one knows for sure.  Some say it is because of the high protein content.  Bloodworms are about 55% protein while most dry fish foods are 32 to 42% protein.  A more plausible answer is that bloodworms have both good a large quantity of protein and the right kind of protein.  Nutritionist would say that bloodworms have a good amino acid profile.  Amino acids are the “building blocks” of protein.  Fish make protein for use in growth, reproduction (making eggs and milt), for cell repair, and various other functions.  Whatever the reason, fish love them.