Guide for Breeding Daphnia magna

Daphnia magna, also known as the large water flea, are small aquatic crustaceans that are ideal livefood for fish. Their cultivation is relatively simple and economical. To successfully raise daphnia after acquiring this great livefood, I have prepared a detailed guide for you.

1. Establishing the culture
a) Tank
Size: For starters, a 10-20 liter tank (aquarium or plastic box) is sufficient. For larger production, you can also use larger containers (50-100 liters).

Material: Glass or food-grade plastic are ideal. Avoid metal containers that may release toxic substances.

Location: Place the tank in a spot with diffused light, not in direct sunlight. A stable temperature is ideal.

b) Water
Type: The best is standing tap water (let it sit for at least 24 hours, ideally longer, to allow the chlorine to evaporate). You can also use rainwater or water from an already established, healthy aquarium.

Temperature: The optimal temperature for breeding is between 18-25 °C. At higher temperatures, daphnia reproduce faster, but have a shorter lifespan.

Hardness: Daphnia prefer moderately hard to hard water. However, they can also thrive in water with a lower pH, around 6.

c) Starter culture
Purchase the starter culture from a reliable supplier, ideally here on ForAquarist from verified breeders. Keep in mind that daphnia are very sensitive to changes in their environment, so they may take some time to acclimate to the new conditions.

2. Feeding
Feeding is the most important factor for successful daphnia cultivation. They are filter-feeding organisms that feed on microscopic algae and bacteria.

Feeding options
a) Green water: This is the best and most natural food. You can prepare green water by leaving water with a little organic matter (e.g., dried nettle leaves) in the sun until it becomes cloudy with green algae.

b) Brewer's yeast: Dissolve a small amount of dried brewer's yeast in water and add it to the tank. Yeast is rich in proteins and vitamins. Dose very carefully to avoid overfeeding and spoiling the water.

c) Yeast: Dissolve a small amount of yeast in warm water and let it stand for at least an hour. Then feed so that the water is slightly "milky." Once the daphnia clear the water, you can add more.

d) Spirulina or chlorella powder: Very nutritious and readily available food. Again, dose very small amounts.

e) Egg yolk: A tiny amount of boiled egg yolk mashed in water can serve as emergency food. However, you must be very careful, as it is very easy to overfeed.

Dosing
Feed small amounts; if you are starting out, it is better to feed twice a day than to add too much food. The water should be slightly cloudy after feeding, but it should clear up within a few hours. If the water remains cloudy for a long time (from my experience - more than a day and a half), you are overfeeding. Overfeeding is a common cause of culture collapse.

Watch how the daphnia move. If they are actively filtering (moving their limbs quickly), they have enough food.

3. Maintenance of the culture
a) Water change
Regularly (e.g., once a week) siphon off sediment and sludge from the bottom of the tank. It is recommended to replace 10-20% of the water volume with fresh, standing water.

Never change all the water at once.

b) Aeration
Daphnia do not need water flow, but gentle aeration helps maintain optimal oxygen levels and prevents the accumulation of organic matter. A weak air stone is sufficient. You can also conduct the culture without aeration, but you must be more careful about the placement of the tank and the number of daphnia.

c) Monitoring the population
Regularly check the daphnia population. If you see many dead individuals, the population is decreasing, or there are few small daphnia, you need to check the water quality and feeding.

Under optimal conditions, daphnia reproduce quickly, and small individuals are visible.

4. Collecting daphnia
Daphnia are best collected with a fine net.

You can catch them directly from the tank and immediately feed them to the fish, or you can keep them in a separate container with fresh water for later use.

5. Common problems and solutions
Cloudy water and odor: Overfeeding. Immediately reduce feeding amounts and change part of the water.

Population collapse: This can be caused by sudden changes in temperature, pH, toxic substances in the water (chlorine, heavy metals), or lack of food. Check all parameters and ensure the water is fine.

Cultivating Daphnia magna will bring joy to any aquarist who wants to offer their fish a natural and nutritious food source. With a little patience and adherence to these guidelines, you will soon enjoy a plentiful supply of these tiny crustaceans.

Successful breeding!