How to Culture Daphnia in Aquariums

Daphnia also known as “Water fleas” is a highly nutritious live food that most aquarists utilize in feeding tropical fish species. The use of live food in aquaculture is mainly due to the rich nutritional value and also the response of fish to catch movements, and this is exhibited in their pursuit of zooplankton.

Daphnia are characterized by high fertility, rapid growth rates, and adaptability, asides that, they are well suited to cultivation in tanks.

These tiny crustaceans will serve as a steady supply of food for your fish and other aquatic animals. So, if you have tried culturing Daphnia but it never works for you, keep reading for more information about culturing Daphnia in addition to guidelines on how to set up and maintain your own Daphnia tank.

Description of Daphnia

Daphnia are planktonic crustaceans that belong to Branchiopoda; a class of crustaceans and consists of four living groups:

• Anostraca (fairy shrimp or sea monkeys),
• Cladocera (water fleas),
• Conchostraca (clam shrimp) and
• Notostraca (tadpole shrimp).

Within the Branchiopods, Daphnia belong to the order Cladocera, whose bodies are enclosed in an uncalcified or bivalve shell known as the carapace.

Daphnia possess flattened leaf-like legs which they use to produce a water current for the filtering apparatus.

The carapace is largely made of chitin, a transparent polysaccharide. The body length of Daphnia ranges from less than 1mm to 5mm (0,04 – 0,2 inches) long.

It has up to 10 pairs of appendages which include the antennules, antennae, maxillae and mandibles; and 5 pairs of limbs on the trunk. These limbs form a mechanism for feeding and respiration, and at the end of the abdomen is a pair of claws.

Note: The genus Daphnia includes more than 100 known species of freshwater plankton organisms found in continents of the world. They exist in a variety of habitats, dominant in fresh and brackish waters, ranging from lakes to ponds and rock pools. However, the most common Daphnia species that are available and utilized by aquarists are the Daphnia magna and Daphnia pulex.

Behavior of Daphnia

The name “Water fleas” stems from the jump-like behavior they exhibit while swimming. The movement of the large antennae produces a quick upward movement of the animal followed by its sinking.

Another behavior is the Diel vertical movement, this involves the movement of Daphnia to the upper levels of the water during nighttime and downwards during the daytime. One of the possible reasons for this behavior is phototaxis-movement of an animal in response to light, either towards or away from a light source, another is predator avoidance.

When food is scarce, Daphnia may browse over the substrate to stir up organic matter or detritus, afterwards, it will consume the suspended particles through filter feeding.

Nutritional Value of Daphnia

Daphnia is a great source of protein, lipids, fibre, and carotenoids.

Depending on their age and the type of food they are fed, the content of proteins in Daphnia can fluctuate between 45-70% while lipids is between 11-27%.

In large quantities, they are enough to meet the nutritional requirements of both juvenile and adult fish.

Setting up a Daphnia Tank

Daphnia starter culture is affordable, readily available, and can be obtained at local fish stores close to you.  

Also, keep in mind that live cultures are easier to make thrive then cysts. So, if you want better chances of success, do not buy Daphnia eggs. Just buy 1 or 2 little bags with live daphnia in your pet store.

Daphnia are pretty hardy creatures. The main reasons why people fail to raise them are foul water, lack of food, and metals (especially copper) in the water. Note: Crustaceans do not tolerate copper well, so be careful with that.

Tank size:

These tiny crustaceans can be raised in containers and tanks as small as 1 – 5 gallons (4 – 20 liters).

However, I would strongly recommend larger tanks with more surface area than depth. Tanks with shallow water depth allow better light penetration for photosynthesis by phytoplankton and provide a large surface to volume ratio for gaseous exchange. In addition, larger tanks also promote the stability of water parameters.

Water type:

Since Daphnia are sensitive to chlorine, you should consider using aged aquarium water (water from an established aquarium), or condition the water before usage to neutralize chlorine and other metals especially if it is tap water.

Personally, I would not recommend using RO/DI or distilled water for culturing Daphnia. Who came up with this idea?! Even though I have read some success stories, it can be very difficult for beginners. The reason behind it is that Daphnia and Moina require minerals in the water; too much of certain kinds can negatively impact them and not enough can be a problem as well.

Therefore, I would strongly advise using only aged and cycled aquarium water from your tanks from water changes.

Important: Do not use Seachem Prime in Daphnia tank. It will absolutely kill a culture.

Water parameters:

It is best to keep the tank indoors rather than outdoors for a more stable temperature and also to mitigate against the invasion of copepods, mosquito, dragonflies and damselflies nymphs.

Always ensure that the tank water is replaced regularly (30 – 50 % weekly) with aged freshwater to keep the ammonia and nitrites level low. Do not forget to siphon the bottom of your tanks.

Temperature: Furthermore, the optimum water temperature for Daphnia is 20 °C (68 °F), keeping the temperature between the range of 18 – 22 °C (64 – 72 °F) is not bad, however, avoid lower temperatures as it may slow reproduction.
pH: A pH between 6.5 and 9.5 is acceptable for most species, with the optimum being between 7.2 and 8.5

Tip: If the water surface has biofilm use tissue to remove it. Daphnia can get stuck in it.

Lighting:

Ideally, try to find a place with bright indirect light. Another option is to provide an artificial lighting source and maintain a photoperiod of at least 8 – 10 hours daily to maximize productivity.

Daphnia show a positive phototaxis behavior. It means they are attracted to the light and spend much time in the upper water level.

Aeration and Filtration:

Also, you should never aerate the Daphnia tank with air stones as air bubbles from these may get trapped in their small bodies thereby causing buoyancy problems.

If you are culturing Daphnia in a community tank, a sponge filter will suffice to provide gentle aeration of the water surface for better oxygenation and suspension of food particles.

However, if you are planning to keep anything else with Daphnia, I would recommend against it, as the filter will pull a lot of Daphnia food out of the water. Instead, you can use the weight from the sponge filter and the uplift tube without the filter, which will work great with just a trickle of air.

Culturing Daphnia in a Shrimp Tank

There are mixed reactions regarding the idea of housing Daphnia with other aquatic animals like shrimp and snails.

Although they contribute positively by cleaning up sediment particles and debris on the bottom, you should also consider the likelihood of something going wrong.

Dwarf shrimp may catch and eat some Daphnia. However, I would not worry about that, Daphnia are no threat at all to the shrimp. Therefore, even if there are some losses, they are so minor that you will never notice them.
Note: Daphnia will not harm the newly born shrimps. They are absolutely safe even for the shrimplets.

The main problems come from feeding Daphnia and potential die-offs. For example, feeding Daphnia without overfeeding shrimp can be a challenge.

That is where aquarists often have some problems. DO NOT think that overfeeding is not a big deal. On the contrary, it is one of the biggest causes of death for dwarf shrimp. 

You can read more about it in my article “How Often and How Much to Feed Shrimp”.

So, if you still want to try keeping/culture shrimp and Daphnia in the same tank, I would recommend keeping a separate Daphnia population in another tank as a “Plan B” in case of a crash or any other problem that may arise.

Feeding Daphnia

As mentioned earlier, Daphnia are filter feeders and they will ingest food particles present in the tank water.

Common food for Daphnia is green water and this can be gotten by culturing microalgae. Alternatively, you can add spirulina powder (pinch should be enough) to your Daphnia tank to turn the water green. A large colony of Daphnia can clear green water in a day, you only need to add more when the tank water becomes clear.

Tip: Put spirulina flakes into a coffee grinder and run until they are pulverized into powder (dust).

Another alternative is active dry yeast; not just any kind of yeast but baker’s and brewer’s yeast (link to check the price on Amazon).

You only need to make a yeast suspension by adding a few grams of yeast to a liter of warm (not hot) water and mix it thoroughly till it dissolves. Next, let it sit for 5-10 minutes before adding to your tank. When you get the bubbles on the top of the yeast – it is ready.

Add a little quantity of the suspension to the culture each day, and you can refrigerate the suspension to preserve it prior to the next usage.

Other food options include:

• infusoria,
• soy,
• pea flour,
• wheat flour (link to Amazon),
• rice flour (link to Amazon),
• garbanzo flour (link to Amazon).

We can mix them together. The food powered mix is pretty flexible, but 1:1:1 ratio works really well.

Note: Lots of aquarists reported that the flour mixture is less crash-prone a food than yeast. Yeast can foul water very easily. So, use it only when you have some experience with that.

Keep feeding schedules consistent and avoid overfeeding, the clarity of the water should be an indicator of how often they need to be fed.

Feed the Daphnia colony regularly and once the water is completely clear, you should feed them again.

How Much is Overfeeding?

Absolutely every article says that it is very important not to overfeed Darhnia. OK… sounds reasonable but how do we know that? Well, they do not say anything.

What I found out is that you have to do two things:

• Monitor your water after feeding. (If you give them the yeast, after a few hours the water should be clean again).
• Test water for ammonia and nitrates. (There should not be any changes).

Therefore, if you see that the water is still cloudy after feeding or your water parameters started changing – these are the sign that you are overfeeding.

Tip: Keeping snails (like Bladder snails, Pond snails, or Ramshorn snails) in a Daphnia tank will help to stabilize the eco-system and will help you against overfeeding. Snails are a balancing component to what makes it successful and sustainable

Gender Differences in Daphnia

Telling the males from the females apart is easy.

1. The brood chamber/pouch is present in the females while the males tend to be about two times smaller than the females.
2. Males also possess larger antennules and first legs; which are armed with a hook used in clasping.

Reproduction and Lifecycle of Daphnia

Water fleas reproduce by cyclical parthenogenesis. It is a mode of reproduction in which phases of parthenogenetic (asexual) and sexual reproduction alternate.

Basically, females reproduce by “cloning” themselves. When there is trouble in the environment daphnia will produce tiny males and reproduce with them making viable eggs.

A female can produce a clutch of amictic eggs after every adult molt. The eggs are placed in the brood pouch situated beneath the carapace. They usually hatch after 1 day but will remain for further development prior to their release 3 days after.

A juvenile Daphnia has to pass through 4 to 6 instars before maturity. Daphnia magna become sexually mature at aged 9 days when the first clutch appears in the brood pouch which are released as neonates at age 11 days.

An interesting fact is that an adult female may produce a clutch of eggs every 3 to 4 days before her demise. A clutch can be up to 100 eggs at once in Daphnia magna (up to 25 eggs in Daphnia pulex) and as low as 1 to 2 eggs in Daphnia cucullata.

Interesting facts: According to the study, the medium lifespan of female Daphnia magna is 83 days. Fecundity declines with age and begins to regress early in the female life cycle at approximately aged 20 days.

Daphnia is capable of producing males and haploid resting eggs in response to unfavorable environmental conditions (freezing or draughts). Furthermore, the eggs are fertilized by the males and enclosed in a protective shell (ephippia).

The resting eggs undergo a diapause and are able to withstand adverse conditions for long periods. Hatching of these eggs is triggered in response to a set of stimuli such as increasing photoperiod and temperature, female offspring will then emerge.

Important: If you do not see babies every day, it means that something is wrong with your Daphnia colony! If the right conditions are met, they multiply like crazy.

Harvesting Daphnia

From time to time, harvest Daphnia from the tank to feed your fish and other tankmates that will benefit from its high nutrient content.

Tip: Before harvesting, make sure you turn off the lighting and aeration so that the Daphnia colony will rise to the surface.

For this process, you will need a fine net or aquarium strainer to sieve out Daphnia from the tank water. Do this in a circular motion and your movements should not be too fast to prevent debris from rising to the water surface.

A few scoops should provide just enough Daphnia for the daily feeding of your fish. You can transfer them directly to your fish tank or store them in a small water container for later usage.

Try to harvest a reasonable amount of Daphnia each time. The point is that too much increase in Daphnia population without adequate harvesting can cause a crash and this situation is more likely to happen in smaller tanks.

Don’t worry about a decrease in population due to over-harvesting. They will reproduce rapidly and fill up the tank again in no distant time.

Be sure to leave enough Daphnia in the tank to keep the population going. You should also delay harvesting if you notice that they are not reproducing quickly like they used to.

In Conclusion

Daphnia is an excellent food source for fish as they provide a high protein (amino acids) and fat content that are vital for growth.

The key of culturing Daphnia successfully is to provide aged water and food. Siphoning the bottom of their containers is very important to remove the dead and uneaten yeast.

My guide will help you in culturing Daphnia that you can harvest daily to satisfy your fish cravings at minimal costs. Now, go ahead and raise a healthy Daphnia colony, be rest assured that your fish will enjoy eating them.

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