Mosquito wrigglers or larvae are the fresh water larval stage of the blood sucking mosquito. They are an ideal natural non-polluting food for most fish species.
Goldfish fry will double their growth rate if they get enough of them.
Fry under a week old struggle to eat newly hatched wrigglers. They can only eat larvae that have just hatched. Within a few hours, the wrigglers grow too big for the fry to eat.
While the fry are under a week old, you want to collect the mosquito egg rafts and transfer them to the fry aquarium. As they hatch, the fry catch and eat the wrigglers.
To collect mosquito egg rafts, you need to create a small stagnant pool of water. The smell of this stagnant water is the key to attracting female mosquitoes that have just sucked blood out of a warm blooded victim. (Blood is required to form the egg raft).
Use a small shallow container and fill it with aged water. In the water put either rotting vegetable matter or a little milk. A bacterial bloom will occur, and the water will start to smell. This smell will attract the female mosquitoes and they will lay their egg rafts on the surface of the water, usually around the sides.
Mosquitoes prefer to lay their eggs in a dark colored container away from any breeze.
The rafts look like tiny canoes and are red/brown in color. The biggest will be about 1/4" (6mm) long. Use a teaspoon to collect the rafts and transfer them to the fry aquarium.
As the fry get bigger, let the wrigglers hatch out and put on some size before transferring them to the fry aquarium.
Mosquito larvae growth rate depends on the temperature of the water. The eggs hatch in one to two days depending on the species and wrigglers will take between 7 and 14 days to reach the pupa stage.
Put each day’s eggs in a separate container with a little scalded lettuce leaf or similar. Keep increasing the days before you feed the wrigglers to your fry as the fry increase in size. This means more fry can be fed with fewer wrigglers; a bonus as the fry will eat all you can provide.
Don't use pea soup green water to raise the larvae in as some suggest. It will kill the larvae because they can't swim in the turbid water because of the long hairs that protrude from their bodies.
I've noticed mosquitoes won't lay eggs in very green water.
Remove any wrigglers that have grown too large for the fry otherwise you won’t be popular with a house full of mosquitoes.
If you live in an area or country where Malaria, Dengue fever or any other serious diseases are carried by mosquitoes, please use some other live food for your goldfish fry.
Be aware that It is illegal to raise mosquito larvae in some countries and states such as California.
For other live food options if wrigglers aren't an option click here.