How to Culture Mosquito Larva

Introduction

Are you looking for ways to bring variety into your fishes’ diet and enrich their lives? If so, you and I have something in common. One of the best ways of accomplishing this is by feeding fish live foods. My hope is that this amateur guide will supply you with all the information you need to kick-start a journey into culturing.

Why Mosquitos?

There are tons of different options for live fish foods, so why opt for mosquitos? I'd argue that mosquito larvae are the most readily accessible, and certainly one of the cheapest if not easiest foods to culture. It's highly likely that you’ve accidentally cultured mosquito larvae at some point or other. Mosquitos are approximately 3500 species strong, and can be found across almost the entire globe. Renowned as disease transmitters, about 3% of mosquito species are known to transmit disease amongst people. While this number may seem small, it adds up quickly - it's estimated that around 700 000 deaths are the result of mosquito-transmissible diseases every year (Malaria, Dengue, West Nile, Zika, and many more).

It is important to note that mosquitos are not born with disease. Illnesses can only be transferred if an adult mosquito feeds from infected host A and carries the disease over to uninfected host B. Larva cannot bite people or other animals and do not present any serious risks when used as live food. There is no risk of larva to human transmission.

If performed correctly, culturing mosquito larvae kills two birds with the same stone; you provide your fish with an improved diet while also preventing the spread of one the world’s deadliest disease vectors. While all we want is the best for our fishy companions, that does not give us license to be complacent. If you live in an area that is at high risk of mosquito related disease or that prohibits the intentional rearing of mosquitoes, I caution against culturing.


Equipment

Minimum required:

• 1-5 gallon tub, preferably wider than tall
• Aquarium water, rain water, or de-chlorinated tap water
• Coffee filter or brine shrimp net
• Small container
• Pipette or turkey baster

Optional:

• Multiple 1-5 gallon tubs
• Fish food/yeast/hay infusion/green water etc.
• Grass/leaves/wood + mesh bag
• Lick mat or small ice-cube tray
• Mason jars/cups and shallow containers (ex. Tupperware or equivalent)
• Clingfilm or equivalent
• Air stone/pump
• Pen and paper or note-taking app

Mosquito Life Cycle




Once female mosquitos take a blood-meal they’ll spend the next 1-2 days preparing to lay their eggs. They prefer to lay in still-water where other mosquitos have already laid eggs or where living larvae are present. Depending on the variety of mosquito, eggs may take the form of little bundles (under 1/4” in length) known as rafts or as singulars called floats that are laid across the water’s surface. These eggs typically hatch into larvae 24-48 hours after being laid. While mosquito eggs can be fed to fish successfully, IME few demonstrate any interest.




Mosquito eggs hatch into aquatic larva, also called “wrigglers". Larvae experience four different moults (the stages between moults are known as instars) as they mature, increasing in size each time. Moults occur within 1-3 days of the previous, thus the complete larval stage can last anywhere from 4 days to 2 weeks. First and second instar larvae are great as fodder for small fry or nano fish such as tetras/rasboras/gourami/guppies < 2” in size, whereas third and fourth instar larvae are better suited for fish in the 3-5” range (or larger). Wrigglers spend the majority of their time feeding (primarily microscopic organisms, phytoplankton, and debris) or hanging at the water surface via siphons, which they use as a kind of snorkel to access air.
Distinctly round bodies and a tendency to dart in short spurts make mosquito pupae or “tumblers” easy to identify. The pupal stage lasts 1-4 days, wherein their energy is directed toward a final moult into adults. Most fish will readily eat mosquito pupae. It is therefore best practice to feed or dispose of your mosquitos at or before this stage of development.


Process

Mosquitos reproduce at different times of the year based on location, temperature, and species. Once you notice mosquito activity in your area, the time is ripe to begin your culture (spring-early summer). Find an area that’s secluded and at least partially shaded. Too much direct sunlight can cause temperature fluctuations resulting in larva die-off. A secluded or partially covered area will help to prevent debris from falling into your tub.
**Debris isn't necessarily unwanted, it will provide a food source for your larva and make the water a desirable location for mosquitos to lay their eggs. On the flip side, it makes harvesting a little more complicated, and gives you less control over what is present in your culture water.**

Once you’ve established a location, fill your tub up with water. Whether you choose to go with de-chlorinated tap water, rain water, or aquarium water is entirely up to you. You’ll find that the aquarium/rain water has a slight advantage over tap as it has already been inoculated with bacteria and detritus.





At this point you’re pretty much done! You can add green water, hay infusion, a pinch of yeast/fish food, floating plants and/or a small mesh bag of dried grass/leaves/wood if you’re inclined, but additions are entirely optional. Mosquitos aren’t too picky about where to lay their eggs, but fostering an environment of bacteria, yeasts, fungi and decomposing matter will make your container more attractive as a prospective mosquito hatchery.

Now we wait. It can take anywhere from a handful of days up to two weeks before you’ll find any eggs or larva (note, you may need to occasionally top-up your culture tub as the water will evaporate with time). You should be checking for activity every single day. Mosquito eggs are difficult to identify with the naked eye and are easily mistaken for dirt. It’s far easier to check for wrigglers than to check for eggs - just give your container a firm shake. With enough disturbance, you’ll notice a scatter of wriggling movement in the water. Congratulations, you’ve cultured yourself some mosquitos! From here there are two routes you can pursue.


Option 1:

The less involved option is to remove your mesh bag/plants/debris and then pour your culture through your filter/net to isolate the larva. Tip: While paper filters can technically be used here, you’ll find reusable filters will be a lot easier to work with.

**Note** This is where a second tub comes in handy. If you want to continue harvesting mosquitos throughout the rest of the season, don’t throw away your culture water! Strain the water and anything you added to the initial tub into a second tub to save yourself some time and energy.

Rinse your larva under fresh water a few times to remove the majority of the culture water and then move them to a separate container of de-chlorinated or aquarium water. Use your pipette to select larva and feed your fish.




You probably won’t be able to feed the entire volume of larva in a single day. In the case of excess, use a silicone lick-mat or small ice cube tray to freeze the remainder for use at a later date. Alternatively, you can keep them alive in a container of aquarium water over the next couple of days (optionally feeding a concoction of green-water/yeast/fish food/etc. as needed). Remember to be on the lookout for pupae. Feed to your fish live, freeze for later, or dispose of them before they fully develop.

Warning for feeding: If you’re feeding your fish larva for the very first time, they may not be prepared for how quickly mosquitos move. You’ll want to introduce the larva one at a time to ensure your fish don’t miss any. This is especially important if you’re feeding lightly stocked tanks or tanks without bottom-feeding fish. After a few rounds, they’ll typically get the memo and you can start adding a few at a time. Mosquito larva are relatively harmless within your aquarium, so if one or two escape, there’s no need to panic. Your fish will eventually catch them. It’s handy to have bottom-feeders in this scenario. A larva's first instinct is to dive to the bottom where they might be better hidden - a school of corydoras or loaches, or even just a handful of ghost shrimp, can take care of any mosquitos that your mid-dwelling fish might not be willing to chase after.
All the same, it’s still better practice to slowly and carefully introduce larva during feeding times to guarantee each has been consumed or use your pipette to catch any runaways. Nobody wants mosquitos flying loose around their home.


Option 2:

The slightly more involved option allows you more control over larva size and presents you with an opportunity to gut-load your mosquitos.

As soon as you notice mosquito activity in your outdoor culture, find some good lighting and scan the surface for rafts and floats. Place any eggs into a mason jar of aquarium water and cover it in a layer of clingfilm (be sure to poke a few air holes in the top). Clingfilm will help raise the humidity and prevent spillage if the jar gets knocked over. Find a location preferably near a window or light source that can mimic a photo-period.

Over the next two days observe the jar carefully. When the two days are up, remove any unhatched eggs and dispose of them. You can then transfer the wrigglers to a larger container filled with about an inch of aquarium water. Mosquitos that hatch within a day or two of one another will typically moult around the same time too. This allows us to keep a relatively controlled container of mosquitos of about the same size and within our home for easy access.






When mosquitos are cultured this way, a thin layer of scum will often develop across the surface of the water. This layer can prevent your mosquitos from accessing oxygen. Keep a close watch on your container, if larvae are struggling to make purchase at the surface of the water, you have a scum layer.

There are a few ways of mitigating this issue:

• Don’t overfeed your culture
• Disturb the scum layer manually, rinse and repeat as needed
• Add an air stone (just remember that mosquitos are built for still-water, you don’t want to toss them around too much)
• Perform small water changes using pipette (and if necessary a filter/net to prevent sucking up larvae)

Diet

In the wild a larval diet consists of whatever resources are available: bacteria, detritus, algae, microorganisms, yeasts, fungi, etc. and while mosquitos can survive on a man-made diet, one that is nutritionally complete has yet to be engineered (to my knowledge).
Green-water. Hay infusion. Kitchen yeast. Crushed fish food. Spirulina powder. Even ground-up pet kibbles work! I feed my mosquitos whatever they can finish in under 12 hours, which will differ based on temperature, stage of development, and larval density.

It will take some experimentation to find what works best for you. I encourage you take note of hatch/moult dates, amount fed, food selection, etc.

When you’re ready to feed your fish, isolate your larvae, give them a good rinse under fresh water and you’re good to go.

Don’t neglect your outdoor culture. Check each day for more rafts/floats and repeat the above process as needed. Any wrigglers in your outdoor culture(s) should be harvested before signs of pupation.

Conclusion

During my initial inquiries into mosquito culturing I found very few comprehensive guides designed for the average hobbyist. My hope is that this article has provided you with the all the necessary tools to begin your own culture in an easily accessible and digestible fashion.
I am always looking for ways to improve upon my practices. If you have techniques or information beyond what I’ve compiled, please share them


All photos and videos are my own.

Below are the resources that helped me while researching and which may help you in turn: