How to Culture Copepods in Aquarium?

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Ah, copepods. Pest to some, a blessing to others. If you’re a newcomer to the whole aquarium business, copepods will surely frighten you at first, given that you have no idea what they are and what they do.

Today, we will discuss copepods and try to shine some light on these ominous organisms that are actually more beneficial than not. So, let’s dive right into it!

What are Copepods?

Simply put, copepods are tiny crustaceans that are virtually omnipresent. They thrive in salt and freshwater environments, and you can find them everywhere.

The reason this sounds like news to you is because you can’t really see them. Well, you can, but they’re tiny, only several millimeters, and nearly transparent, making them almost invisible to the naked eye.

These organisms vary wildly in terms of biology, as some live on the ocean floor, others inhabit marine waters, and several others are parasitic in nature.

But today, we will discuss the standard copepods that are likely to inhabit your tank and why they are actually beneficial to the ecosystem.

More specifically, we will discuss reef tank copepods, since these are the ones that should interest you the most.

That being said, whatever applies to marine copepods applies to freshwater ones – just a heads-up.

What do Copepods Eat?

Aquarium copepods specialize in consuming phytoplankton and benthic (located on the ecosystem’s bed) detritus and algae residues.

These voracious creatures are deemed the locusts of the sea due to their unhinged appetite and feeding behavior.

Copepods consume individual cells of phytoplankton and can devour in excess of 370,000 cells within 24 hours.

These organisms are active swimmers, with one copepod covering a water volume of at least 1 million times its body volume every day.

They are relentless in their search for sustenance, which makes them a great addition to any saltwater or freshwater setup.

They will also spread fast if the food is abundant, which may not be ideal due to their impact on the tank’s esthetics.

After all, the water just doesn’t look the same with all those tiny organisms swimming everywhere.

So, I understand why most inexperienced aquarists freak out and want to get rid of them. However, as you will soon see, that’s not advisable.

How to Start a Copepod Tank?

An even better question would be – why would you start a copepod tank? The answer is as simple as they come: because you need copepods.

These micro-crustaceans consume detritus, phytoplankton, and algae growing on the tank bed and various hard underwater surfaces. Their activity keeps the tank water clean and contributes to a fresher and more stable environment.

This is great for your corals, fish, and pretty much all tank inhabitants.

Not to mention, copepods are harmless since they don’t affect water quality (more on that later), and they don’t cause any harm to fish.

Not to mention, many fish species actively hunt and eat copepods since they are rich in protein and fats.

Now that you understand the copepods’ role and importance, it’s time to start your own copepod culture. This is necessary due to many fish’ appetite for copepod meat, which can lead to copepod extinction in your aquarium.

And you don’t want that for all the reasons we’ve already mentioned.

To start your own self-sustainable copepod tank, consider the following requirements:

  • The right container – The size and type of the container you’re using depends on your copepod culture’s size. A 5-10-gallon aquarium should cover most situations.
  • Crafting the setup – Go for a sand bed and use live rocks for proper natural filtration. An air stone is also necessary to ensure optimal oxygenation and provide some water movement. I would advise against using a standard filtration system. Copepods are small organisms that can easily get sucked into the filter. Plus, you don’t need artificial filtration in a 5-10-gallon setup. A good airstone, paired with a decent live rock, should do all the work instead. Add some compact grazing surfaces as well to provide your copepods with open eating areas.
  • Add a food source – I recommend microalgae as a long-term food source for your copepods. So, you should set up your aquarium to promote the development of microalgae while accommodating the copepods at the same time. Phytoplankton is another great nutrient source, especially since it’s easy to grow at home. Just remember to check ammonia and nitrite levels constantly in your tank. That’s because copepods will never overeat, which means that all the excess food will decay in the water.
  • Lighting – Copepods have no need for bright lights, so keep them dim to preserve your copepods’ comfort. Make sure there’s enough light to promote the growth of microalgae since these make for the ideal growth medium for your copepods.
  • Mind the temperature – Copepods are comfortable at temperatures around 72-82 °F. These are standard temperatures for most aquarium fish, so they shouldn’t be difficult to reach and maintain. Don’t let environmental temperatures jump over 85 °F since that will cause mass death among your copepod population.

Once the environment is set up, you know to begin the next phase, which is maintenance.

How to Maintain a Copepod Culture?

Fortunately, the maintenance part is minimal, as an optimized copepod ecosystem is pretty much automatic. You only need to perform monthly water changes to preserve water quality and freshen up the system.

Copepods don’t produce too much waste. Plus, you will collect the tiny crustaceans regularly to feed them to your fish or replenish the copepod population in the main tank.

You only need to perform extra water changes in case of overfeeding your copepods which can result in ammonia and nitrite spikes.

Other than that, your involvement is minimal, only requiring general supervision.

How do Copepods Reproduce?

The reproduction system in copepods is pretty straightforward. Copepods reproduce sexually, with the male chasing the female and inserting its sperm in the female’s specialized pouch.

There, the sperm will fertilize the eggs, which the female will place into a sack and deposit them somewhere in the environment.

The hatching larvae are called nauplii, which represent the first stage in the copepod’s life cycle.

These nauplii undergo molting to turn into copepodite, which are essentially copepod juveniles. These will then mature into adults, resetting the entire life cycle.

Copepods reproduce fairly fast, but the entire life cycle can last several months. After all, these tiny crustaceans can live between 6 months to a whole year in good conditions.

How to Harvest Copepods?

You only need a syphon with a fine mesh attached to the water outflow for the job. The mesh will trap all of the copepods for ease of collection.

You can get as many as you want and allow the rest to carry on with their routine to multiply and replenish the ones you’ve collected.

How do You Know if Copepod Culture is Dead?

You can tell that the copepod culture is dead if none of them is swimming anymore. In a tank with hundreds of copepods, you should see their bodies accumulating in bulk on the substrate.

If you only have a handful of copepods swimming with hundreds or thousands dead on the tank floor, that’s a sign that the culture is nearly dead.

You can consider the culture officially dead if no live copepods are visible anymore. Fortunately, this scenario is unlikely if you manage the culture properly.

Monitor water quality constantly, adjust water parameters based on your copepods’ needs, and ensure sufficient food and your copepod culture will thrive.

What Fish Will Eat Copepods?

Given that copepods are omnipresent in any aquatic system, it’s safe to say that nearly all fish consume copepods. Some, however, eat them more effectively than others and are inclined to hunt the tiny crustaceans.

Among the most popular copepod killers, we mention clownfish, rasboras, neon tetras, Endler’s guppies, cardinal tetras, and many others.

Conclusion

Copepods are a welcome addition to any aquatic setup, and you can’t have enough of them. That being said, they do make for an uneasy picture when flooding the tank water.

If you want to control the copepod population, add some copepod eaters to your aquarium.

Then set up a copepod culture to keep the crustacean population alive in case your fish go overboard with all the hunting.

This is a great strategy for reef tanks, but it also works great for freshwater setups.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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