Research Paper to Read: (1992) Culture Techniques of Moina: The Ideal Daphnia for Feeding to Freshwater Fish Fry

Source: Science Direct or IFAS.
This is not a research paper in the traditional sense but a published guideline from fishery experts.

What are the key point here?
(1) In term of size, adult Moina is on average is around 700 - 1000μm and for young Moina, average around 400μm. A small size Moina is only slightly larger than Rotifier and smaller than Brine Shrimp. For that reason, Moina is preferable compare to Brine Shrimp as it can live longer in freshwater. (Note: Which is why some Betta sp. breeders only use Moina as the only live feed for all life cycle of the fish)

(2) As Moina is tolerant to poor water quality, it's generally found in any water sources (pools, ponds, lakes, ditches, slow-moving streams, and swaps) polluted with sewage.

(3) Moina strives in temperatures between (24°C - 31°C) but also can tolerance in extreme temperature of (5°C - 31°C) which is suitable for culturing in most part of the world.

(4) Moina feeds on several food sources of bacteria, yeast, phytoplankton, animal manures, detritus (decaying animals or plants), and blue-green algae Microcystis aeruginosa.

(5) Moina reproduces either in sexual or asexual (more common) way. Sexual maturity is around 4 - 7 days with brood size of 4 - 22 per female every 1.5 - 2 days. Each female can produce around 2 - 6 broods in its life span.

(6) Population wise, Moina have higher density (19000 individuals per gallon or 5000 per litre) compare to Daphnia (1900 per gallon or 500 per litre). Production density of Moina depends on food sources. Cultures fertilized with yeast and ammonia nitrate yields 106g/100m3  and compare to Daphnia with similar food source, 25 - 40g/m3. Meanwhile, Moina culture fertilized using organic fertilizer yields even higher output of 375g/100m3.

Why this paper?
The importance of Moina and Daphina as live feed have been discussed in separate post and I will not go details into that. As mentioned, this paper serves as a good introduction and guideline to Moina, the species itself, and most importantly, the culturing techniques in maintaining a Moina population. Moreover, this paper also suggested that Moina is a better live feed compare to Daphnia and Brine Shrimp due to its reproduction volumes and life span in freshwater.

Material and Methods
If you need specific quantity of Moina per day, the suggested method is to batch culture. In batch culture, a new culture is started every day in a separate container. Harvesting should be done around 5 - 10 days where all the food have been consumed by the Moina. Starting new culture every day have another benefit where isolation can prevent contamination due to other Zooplankton or predators.

The previous culturing method combines Moina's food source and its population. Another approach is to use separate culture of food source and Moina population. There are two tanks, the food source or Phytoplankton/algae tank and the Moina culture tank as illustrated below. This setup have the advantages of reducing contamination and sharing of algae tank with multiple Moina tanks. However, extra spaces is needed for such layout.

The next part is on the discussion of the setup and equipment. We start with container, water, aeration, and feeding or fertilizing. Then we proceed with inoculating, monitoring, and harvesting.

38 litres culture tank can only produce enough Moina for hobbyist. For mass production, larger and multiple containers should be used. Water height for the tank should be optimally around 0.4 - 0.5m and can be stretched till maximum of 0.9m. No direct sunlight over the tank and should be some shades to reduce the sunlight till 30% till 50%. To clean up the tank, it should be disinfected with 30% solution of muriatic acid or sun dried.

As Moina is very sensitive to water content, extra care should be taken to prevent poisoning the culture. Anything that contains pesticides, metals, detergents, or bleaches should be removed or discarded before starting the culture. Different water sources have different treatments as shown below:

(1) Well water: aerated for two hours.
(2) Tap water: aerated for two days together with dechlorizer.
(3) Natural spring water, rain water, lake water, or stream water: use as it.

The water temperature in the culture tank should be kept optimally around (24°C–31°C). Anything out of these range will reduce the production of the culture.

Aeration oxygenates the water, suspends food particles, and increases Phytoplankton productions. Apply gentle aeration with no small bubbles as it can cause Moina to trap under the carapace which make it float at the surface and thus killing it.

Feeding or Fertilizing
Different culture medias affects the production of the Moina colony and can be categorized into organic fertilizers and mineral fertilizers. For a 397 litres of water, the quantity (Note: I only keep the metric measurement) that should be added initially for the culture for each fertilizer is shown below. Repeat and replace 50% or 100% of the same ratios after 5 days later.

(1) Yeast: 8.5 - 14.2g of baker's yeast.
(2) Yeast and mineral fertilizer: 8.5 - 14.2g of yeast, and 14.2g of ammonium nitrate.
(3) Alfalfa, bran, and yeast: 42.5g of alfalfa pellets or meal, 42.5g of wheat or rice bran, and 8.5 g of yeast.
(4) Cow manure or sewage sludge, bran, and yeast: 142g of dried manure or sewage sludge, 42.5g of wheat or rice bran, and 8.5g of yeast.
(5) Cow manure or sewage sludge, cotton seed meal, and yeast: Use 142g of dried manure or sewage sludge, 42.5g of cotton seed meal, and 8.5g of yeast.
(6) Horse or cow manure or sewage sludge: Combine 567g of dried manure or sewage sludge.
(7) Chicken or hog manure: Combine 170g of dried manure.
(8) Yeast and spirulina powder: 6g baker's yeast, 3g spirulina powder. Mix with warm water and let it sit for 30 minutes. Pour the mixture through a net into the Moina culture to filter out unresolved yeast.

For hobbyist, the culture medias of item (1), (2), (3), and (8) is more suitable and readily available, especially for indoor environment.

This process is to introduce organisms, in this case, Moina into a culture medium. Typically we call this a Moina starter culture. Start with 100 Moina per litre. Typically inoculation starts after 24 hours or more after fertilization except for yeast with aeration. We can add the Moina after a few hours.

How do we make sure that the Moina culture is healthy and if not, proceed with some adjustments? There are four ways:

(1) Extract one tablespoon or 15ml from the culture and examine with magnified glass or microscope. Pay attention to the colour, intestinal tracts, and movement. In a healthy culture, Moina are green or brown-red in colour with full intestinal tracts and active movement. Unhealthy culture due to environment or insufficient food will produce Moina pale in colour with empty intestinal tracts or resting eggs.

(2) Extract one teaspoon or 3 - 5 ml sample and kill it with 70% alcohol solution. Count the Moina using magnified glass or microscope. If there are 45 - 75 Moina, then the culture is ready for harvesting.

(3) Slightly cloudy, tea colour, or green colour water means there are still food source available for Moina. Only clear water, with transparency of 0.3 - 0.4 m, indicates insufficient food available and need to be replenished with 50% - 100% initial quantity when fertilizing.

(4) Discard the culture and start a fresh new one if the current culture have been infected with predators like Hydra, back-swimmers, diving bettles, or dragonfly larvae.

Use netting net with 50 - 150μm mesh or coffere filter to collect and harvest Moina. For semi-continuous culture, only extract about 20% - 25% from the culture tank. After harvesting, do a partial and small water change and stir the bottom sediments while at it. Moina can kept alive in clean water and fridge for several days with some lost of nutrients due to starvation. For long periods storage, harvested Moina can be kept by freezing in low salinity water (7ppt, 1.0046 density) or freeze-drying. While frozen Moina still retains its nutrient value, it will leach out rapidly upon exposure to water. Enzyme is lost within ten minutes. Amino acids and bound amino acids will lost after one hour.



What you're going to do with the knowledge you've gained?
(1) Buy several Moina starter from different breeders or aquarium shops.
(2) Start two small Moina cultures either in indoor and outdoor environment using plant detritus (decaying water organic matter), alfalfa, bran, yeast, and spirulina powder.

What are the further unsolved questions?
(1) What are the available published literatures on mass scale Moina or Daphnia production?
(2) There are many species of Moina and which species is the most suitable for larviculture?
(3) How do we aerate water without create any bubbles?

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