They spend a couple to several weeks growing after hatching from a gelatinous egg mass which
looks too much like some mucus attached to the edge of water filled containers. They develop into mouthless gnats which have about a week to fly around, mate and reproduce on suitable water. Not much of a social life!

They have been brought into houses as larvae when crazy aquarists lug an outdoor daphnia culture indoors for the winter. January or February "heat waves" outdoors seem to stimulate their transformation into mosquito-like gnats indoors - thereby creating some unnecessary anxiety among family members.

They (the bloodworms, not the family members) build mud cases around themselves and can be wiped off of the side of culture containers or shaken off of the rotting leaves they feed on. On hot summer days they wiggle themselves to the surface and can be easily netted.

They hatch out in such numbers that they form clouds resembling smoke over lakes and ponds on
summer evenings. Many bottom feeding fishes count on them as important food items.

Collectors must net quantities of bottom mud and rinse them out of the mud through fine meshes. This is why most American hobbyists don't seek to culture them.

By the way, don't feed live foods taken from waters with fish in them. Live foods virtually never carry diseases. However if they come from waters with fish, they may be secondary hosts for a variety of fish parasites.

I have used three brands of frozen blood worms on the advice of other fish heads who felt that
they were especially carefully packaged. The San Francisco Bay brand cubes of blood worms yield worms which are pretty large for all but the biggest guppies, but they are great for the next sizes of aquarium fish.  

Haikari and locally produced Fish King blood worms are more managable for guppies. They are a great "meaty" conditioning food.

There are a couple of draw backs which you should know about. One is that they must stay frozen until used.

Defrosting and refreezing can ruin the product. Evidentally in a case with at least one off brand - where there was spoiled material to start with, spoiled b.w. can be lethel to your fishes.

Probably producers and pets shops have also been blamed for bad blood worms where it was the aquarists who let them defrost and then refroze them after too long a time.

Let the frozen portion of blood worms defrost in luke warm water. Gently rinse them through a net or small meshed seive.

Goofy as it sounds, if you are worried about their quality, check at a distance to see if they smell foul (when nobody is watching.) If they smell that way, don't use them. (That is why I go with proven brands and take care not to let them defrost before they are needed.)

Here's the tricky part. Don't breath the dust from freeze dried blood worms or even touch live, freeze dried or frozen blood worms much. There is evidentally something in their composition which can cause a few lucky souls severe allergic reactions. Several aquarists have had trouble breathing after touching bloodworms.

If they have then rubbed their face, more trouble can result. At least one person has had to be rushed to the emergency room according to a killilist posting. Who wants to have, "He departed this world after feeding the fish!"

I have had asthma for about a decade and have never had trouble with frozen or live blood worms. (I decline to tempt fate with freeze dried anything anymore.)

Most runs to buy frozen foods at a LFS include a small cooler with one of those gel refrigerant
packs. A section of newspaper is placed between the frozen material and any bags of live blackworms, glassworms or the rare brine shrimp. That way everything gets home intact.

After the defrosting process mentioned above, the blood worms are put in a jar of seasoned water. Most aquarists use a turkey baster to carefully squirt the right quantity into each tank. (If one can find good basters in the stores at the moment please let me know where.) Sometimes I scrub down hands with baking soda afterwards.

Freeze-dried dried foods still have a lot of their food value. They are proportionately cheaper than frozen foods and they obviously are more convenient to store. If you feed them, just be careful not to breath the dust and rinse off your hands afterwards if need be. (Just what one wants on their resume - snorting fishfood!)

One wouldn't stop driving gasoline powered cars just because gasoline explodes. Likewise most
aquarium foods and variety are beneficial to your fish and useful to aquarists with wise use.