Moina are a type of freshwater zooplankton that can also be used as a live food source because they are nutritious and ideal for feeding small fish, fry, and crustacean larvae.
Moina are also one of the easiest live foods to culture at home in small containers. With a basic setup and proper care, aquarists can produce a regular supply of Moina to feed out to their fish.
In this article I will describe what Moina are, their life cycle, and reproduction. I will also cover details on setting up Moina culture, feeding and maintaining optimal water conditions, generating dense populations, etc.
Moina as Live Food
- Nutritional value. Moina contain high amounts of protein, lipids, and other nutrients essential for fish growth and health.
- Hunting behavior. Their tiny size and constant movement trigger feeding responses. Fish and fry enjoy hunting for the Moina.
- Convenience. Moina are way simpler to culture at home than many other types.
- Cost. Maintaining your own Moina culture is inexpensive compared to buying live foods.
Nutritional Value of Moina
As I have already said, Moina are rich in high-quality proteins, beneficial lipids, vitamins, and minerals. It supports growth, health, coloration, and development in aquarium fish.
Additionally, their soft bodies are also easily digested by fry, which allows efficient absorption of the nutrients. All in all, it makes Moina an excellent live food choice even compared to other great live feeds such as Rotifer and Artemia.
- Protein. Moina contain high levels of protein, ranging from 50-60% of their dry weight. This protein is rich in essential amino acids like lysine, tryptophan, and methionine.
- Fat. The total amount of fat per dry weight is 20%–27%.
- Lipids. Total lipid levels range from 10-22% of dry weight. The lipids consist largely of neutral fats along with some phospholipids and sterols like cholesterol.
- Carbohydrates. Carbohydrates make up 5-12% of dry weight, in the form of sugars and polysaccharides.
- Vitamins. Moina provide B vitamins like B12, B1, B2, B6, biotin, and folate. They also contain antioxidants like carotenoids.
What are Moina?
Moina are a genus of small aquatic crustaceans belonging to the family Moinidae. They are a type of freshwater zooplankton.
Moina are sometimes referred to as “Water fleas”, although they are not true fleas. This comes from their jerky, flea-like movements when swimming.
There are nearly 50 recognized species of Moina worldwide today with Moina macrocopa being the most commonly used for aquarium culturing.
|Etymology: Moina is derived from the Greek word “Moina”, meaning “Marine animal” or “sea calf.” The genus name Moina was first applied to these small crustaceans by Jurine in 1820.|
Natural Habitat of Moina
Moina are cosmopolitan, found on all continents except Antarctica, and most diverse in tropical regions.
In the wild, Moina are found in a variety of freshwater habitats such as marshes, ponds, lakes, pools, roadside ditches, slow rivers, etc. Some species, for example, Moina macrocopa can tolerate even slightly brackish waters.
Moina usually stay near the surface and avoid deep waters. The stagnant, nutrient-rich (with phytoplankton and zooplankton) water allows rapid population growth.
Description of Moina
- Size. Moina are tiny crustaceans, measuring 0.008-0.02 inches (0.2-0.5mm) in length as adults. They are approximately 2-3 times smaller than the maximum length of Daphnia, and about 2-3 times the length of rotifers.
- Body shape. The body is oval-shaped and moderately compressed laterally. The head is fused with the body.
- Antennae. Two pairs of antennae are present. The first pair is small. In males, these antennae are armed with 3-6 hooks at the tips, which are used during mating to grip the female. The second pair is very large, extending the body length, and used for swimming.
- Carapace. There is a dorsal transparent carapace or shell that covers part of the body. It is thin and flexible.
- Brood chamber. Females have a dorsal brood chamber under the carapace for carrying eggs and embryos.
- Color. Moina are usually transparent or tan, with some reddish-brown pigmentation. The gut may appear greenish from ingested algae.
Lifespan of Moina
Under optimal conditions, the average lifespan of Moina is about 2-3 weeks. During this period, they can molt about 15 times.
In warm water, they have a shorter lifespan due to an increased metabolism. However, at cooler temperatures, Moina may survive for 1-2 months.
Note: Maximum lifespans up to 70 days have been observed in a laboratory setting.
Life Cycle of Moina
Their life cycle typically involves 4 stages: egg, nauplius larvae, juvenile, and adult.
- Eggs. Females usually produce eggs parthenogenetically without being fertilized. Each female can produce 4-22 eggs every 1.5-2 days, allowing exponential population growth.
- Nauplius Larvae. Eggs hatch into free-swimming nauplius larvae after 1-2 days. Nauplii have underdeveloped bodies without a carapace. They molt and grow over 2-3 days through several naupliar stages to become juveniles.
- Juveniles. At the juvenile stage, they resemble small adults. They develop full carapace and mature appendages. This period lasts 3-5 days. For Moina macrocopa scientists distinguish, on average 1–3 juvenile stages.
- Adults. Moina reach adulthood in about a week after hatching. Their reproductive period lasts about 7-19 days, after which they die. According to the study, in the adult stages, molting cycles occur after each hatch.
Note: At warm temperatures of 77 – 86°F (25 – 30°C), each generation of Moina takes roughly 2-3 days from egg to adult.
Reproduction of Moina
Moina reproduce through 2 types:
- Primarily asexual reproduction (parthenogenesis),
- sexual reproduction (situational)
Parthenogenesis is a form of asexual reproduction where females produce amictic (asexual) eggs without mating that develop into clones of the mother. The eggs are released from a pair of ovaries into a brood pouch, located dorsally.
However, under stressful, overcrowded, or deteriorating conditions (including lack of food) Moina reproduces sexually. Male Moina are rare and smaller. Their main role is to fertilize mictic eggs for genetic recombination. Mictic eggs become either male or female.
Sexual reproduction facilitates genetic recombination until circumstances favor renewed population growth through normal parthenogenesis.
- Resting eggs. Females may produce thick-shelled resting eggs that can survive harsh conditions and hatch when favorable.
- Temperature impact. Higher temperatures favor amictic egg production while lower temperatures induce mictic eggs and males.
Behavior of Moina
- Swimming. Moina are constantly swimming using their large second antennae in short, rapid jerks giving them a hopping or darting motion. Their constant movement triggers feeding responses in fish.
- Feeding. They filter feed on phytoplankton and microorganisms. The feeding appendages create a feeding current that draws in food particles.
- Vertical migration. Although Moina spend most of their time suspended in open water. They also migrate up and down through the water column each day, ascending at night and descending during the day. This avoids visual predators.
- Phototaxis. They exhibit phototaxis, moving toward light sources. This helps concentrate food populations through light-mediated aggregation.
- Molting. To grow, Moina regularly molt their exoskeletons, leaving themselves vulnerable until new shells harden.
- Dormancy. Under harsh conditions, Moina produce dormant resting eggs that can survive for lengthy periods until hatching cues like temperature and light trigger emergence.
DIY Set-Up for Moina Culture
- Culture starter. A small amount of live Moina.
- Container. A small tank or plastic container/bucket/bottle (1-2 gallons or 4-8 liters will be more than enough for ordinary hobbyists). It should be transparent for easy viewing.
- Water. Pre-aged and dechlorinated tap water. The water should have a neutral pH.
- Alkaline buffers. For example, crushed coral, crushed oyster shells, limestone-based rock, reef tanks sand, etc.).
- Food source. Powdered spirulina, yeast, alfalfa powder, or liquid fry food to feed the Moina.
- Aeration.An air pump and flexible airline tubing.
- Harvesting tools. A plankton net, brine shrimp net, or coffee filter to collect the Moina.
- Light source (optional). Natural or artificial lighting to promote algal growth.
- Prepare the container. It should be clean, and free of contaminants.
- Prepare water. Fill the container with warm pre-aged dechlorinated freshwater.
- Install Aeration. Set up an air pump to provide gentle aeration. This helps keep the water oxygenated.
- Add food. Add powdered spirulina (yeast, etc.) as a nutritional boost.
- Add the culture: Introduce Moina starter culture.
Although it can be easy to culture them, Moina are not very hardy animals. So, it is better to avoid extremes in water quality.
- pH. They prefer a pH between 7-8.5, with optimal growth around 7.5-8. Moina do not like acidic water. Therefore, if you have such water you will need to use alkaline buffers.
- Hardness. Moderate hardness between 3-10 GH (50-150 ppm) is well tolerated. Very soft or hard water will limit their growth.
- Temperature. Some species of Moina are resistant to extremes in temperature and easily tolerate variations from 41–88°F (5–31°C). Nonetheless, the ideal temperature range is 70-85°F (21-29°C). Cooler temperatures below 60°F (15°C) slow reproduction. Heat above 90°F (32°C) shortens lifespan.
Note: Experiments showed that, at 50◦F (10◦C), only the mature females survive for 4–5 days. The young offspring set free die a few hours after their birth. At 95◦F (35◦C), no ovigerous female survived for more than 24 h.
- Oxygen. Some aquarists do not use it since Moina require very little oxygen. At the same time, experiments showed that by keeping food particles in suspension, we increase phytoplankton production. As a result, females produce more eggs. So, it is highly recommended to set up an air pump to provide gentle aeration.
- Salinity. Moina do best at salinity 0. According to the study, the survival rate of Moina macrocopa at salinity 15 was approximately 20%.
Note: Moina are extremely sensitive to pesticides, metals (such as copper and zinc), detergents, bleaches, and other toxic materials in the water supply.
In the wild, Moina eat microalgae, bacteria, and detritus. As a matter of that, Moina are one of the few zooplankton which can eat the blue-green algae.
In aquarium conditions, good food options include:
- powdered spirulina,
- brewer’s yeast,
- liquid fry food,
- rice bran,
- wheat flour,
- animal manures (i.e. chicken manure, pig manure, and cow manure),
- fermented rice bran, etc.
Moina eat between 50-200% of their body weight in food particles daily. So, feed the culture small amounts of powdered food every day.
Tip: Add a pinch of fertilizer or dried manure to stimulate algae growth, which Moina will graze on. Green water is also great for culturing Moina.
How to prepare food:
- take a clean glass,
- pour in a small amount of aged and dechlorinated water,
- add some food (pinch is enough),
- mix it thoroughly,
- pour the mixture into the growing culture.
|Important: Do not overfeed to prevent fouling the water. Overfeeding can crash a culture. Feed more when density is high. Cut back when populations decline.|
Maintenance of Moina Culture
|Very Important: Moina populations reproduce in bursts. So, there is a very high chance that after some time (usually 1-2 months) the quantity will suddenly decrease sharply, sometimes even disappearing completely. So, it will be necessary to restart the culture.
Therefore, always have backups. Ideally, you need to have 3-4 cultures at the same time.
- Keep your water warm. Moina will reproduce quickly in warm water.
- Check culture density daily. They slow down reproduction in high densities.
- Siphon out any uneaten food accumulations at the bottom to prevent fouling.
- Keep notes on feeding schedules and responses to refine the diet and culturing methods.
- Control nitrates and It is believed that high concentrations are the main cause why the culture can crash. Do small water changes.
- Always have backups. Ideally, you need to have 3-4 cultures at the same time.
- If you see that they stop not reproducing well, the culture should be completely harvested and a new culture started.
|Overcrowding, overfeeding/starvation, buildup of waste products, and introduction of predators/pathogens can rapidly kill off individuals and crash a Moina culture.|
Moina reproduces extremely fast. So, in 1-2 weeks after setting up, the culture can have a 100-fold increase in biomass, turning the water greenish-brown. Thus, it is time to harvest Moina. It is better to do this during daylight hours when Moina are suspended in the water column.
- Turn off the aeration and allow the food particles to settle.
- Take a fine mesh net/strainer. Nets with mesh around 0.3mm work best to retain Moina.
Note: The coffee filter is also good enough.
- Scoop the net through the 20-30% culture while letting water pass through.
- Rinse harvested Moina in a bowl of clean dechlorinated water.
- Feed to your fish.
- Jars or small bags to store harvested Moina for feeding out over the next 1-2 days.
Results of the experiments showed that after reaching a certain level of density, egg production drastically decreases.
Moina are a cost-effective, nutritional live food to raise healthy, vibrant fish. Culturing your own sustainable supply is quite simple even with a basic home setup.
Their rapid reproductive cycle, combined with proper harvesting and maintenance will allow you to utilize this fish food almost indefinitely.
Therefore, it is very surprising that culturing Moina is not as popular as, for example, her closest competitor and relative – Daphnia.
Moina as Live food
|Simple and easy to cultivate||Suitable only for small fry and larvae|
|Extremely fast reproduction||Requires constant maintenance/restarting|
|Excellent nutritional value|
|Stay in the middle and upper water column|
- Baird W.Genus Moina // Natural history of the British Entomostraca. — London: Ray Society, 1850. — С. 100—102. — 364 с.
- Bekker E. I., Karabanov D. P., Galimov Y. R., Kotov A. A. DNA barcoding reveals high cryptic diversity in the North Eurasian Moina species. — 2016. — Т. 11, № 8. — С. e0161737.
- Martinez-Jeronimo, Fernando, and Alejandra Gutierrez-Valdivia. “Fecundity, reproduction, and growth of Moina macrocopa fed different algae.” Hydrobiologia222 (1991): 49-55.
- Benider, A., A. Tifnouti, and R. Pourriot. “Growth of Moina macrocopa (Straus 1820)(Crustacea, Cladocera): influence of trophic conditions, population density and temperature.” Hydrobiologia468 (2002): 1-11.
- D’Abramo, Louis R. “Ingestion rate decrease as the stimulus for sexuality in populations of Moina macrocopa 1.” Limnology and Oceanography25, no. 3 (1980): 422-429.
- Yuslan, Amirah, Sharifah Najuwa, Atsushi Hagiwara, Mazlan A. Ghaffar, Hidayu Suhaimi, and Nadiah W. Rasdi. “Production performance of Moina macrocopa (Straus 1820)(Crustacea, cladocera) cultured in different salinities: the effect on growth, survival, reproduction, and fatty acid composition of the neonates.” Diversity13, no. 3 (2021): 105.
- Forro Korovchinsky, N.M.; Kotov, A.A.; Petrusek, A. Global diversty of cladoceran (Cladocera; crustacean) in freshwater animal diversity assessment. Hydrobiologia 2008, 595, 177–184.
- Kamrunnahar, Kabery, Anisuzzaman Md, U-Cheol Jeong, and Seok-Joong Kang. “Mass culture of Moina macrocopa using organic waste and its feeding effects on the performance of Pagrus major larvae.” The Egyptian Journal of Aquatic Research45, no. 1 (2019): 75-80.