Copepods, small crustaceans found in ocean habitats, play a pivotal role in the aquatic food web and have a significant impact on the health of reef tanks. These microorganisms are not just food for fish; they help maintain a balanced and healthy aquarium environment. But how important are they really? The results will likely surprise you as we walk away with a much better understanding of how to set up our reef tanks for the best possible results. 


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We chose to use Algaebarn and their popular Ecopod Blend which contains 4 different pod species. Having this variety of pod species should help us obtain the maximum benefit in terms of diversity, pest predation, and competition for resources. 

  • Tigriopus californicus
  • Tisbe biminiensis
  • Apocyclops panamensis
  • Oithona colcarva

A single 16oz jar of Ecopods contains upwards of 7000 live pods. Since we didn't want to wait for healthy populations of copepods to establish in the tanks, we overdid it and added a total of 16 jars of Ecopods to each of the 12 tanks. This way, we could be certain a healthy population of pods was active and the results could be observed right away. As expected, over 100,000 live pods per tank most certainly made an impact.

We observed the tanks for 4 additional weeks after adding the pods. Some tanks responded favorably while others still struggled with pests, some were virtually unchanged. The video above covers the results of each test tank individually. For the purpose of this writeup, we'll cover the answers to the most important questions. The questions we can ALL use to produce more favorable results in our own aquariums. 

How can pods help me produce better results in my tank?

Adding pods early, before lights and the addition of fish and clean-up crew animals is the best way to give the pods a fighting chance at establishing a very stable population. The pods create competition and even consume photosynthetic pests as they are ultimately introduced alongside livestock. If one thing was clear throughout the test tanks it was that diverse, balanced biomes that contained microcrustaceans were much better equipped to handle pests than those without. 

In well-established aquariums, many pod species are scavengers and prey upon phytoplankton, diatoms, microalgae, and even detritus which ultimately helps keep the aquarium clean. They are a fundamental part of the natural food chain in your aquarium and help with the recycling of nutrients. Even if you already have pods, introducing new species (within reason) can help fill individual niches and ensure you have the best possible diversity and defense against photosynthetic pests.

Copepods work alongside your clean-up crew invertebrates and herbivorous fish to create a redundant biome. While it's a good idea to avoid the introduction of photosynthetic pests early on, approach your tank with the mindset that these pests will exist and do everything you can to prevent pests with redundant protections. 

How many jars of copepods should I add to my tank?

When seeding a new aquarium that does not contain any fish, flatworms, or other organisms that will prey upon the pods, one 16oz jar per 30 gallons is the minimum recommendation for seeding the tank. In time, the populations will stabilize based on available food sources and predation. As the tank matures, you can add refreshers on an annual basis to ensure a diverse and viable population is maintained. 

If your tank is experiencing a diatom bloom and/or contains predators that will prey upon the pods, the more the merrier. Adding something like one jar per 15 gallons will ensure you start with a viable foundation. Regardless, the population of pods will stabilize over time based on available resources and the amount of predation in the tank but giving them an abundant start will only prove to be beneficial.   

Add the pods to your tank at night after the fish have been fed and the lights go out. This gives them a better chance of finding a safe haven in the rocks and substrate. 

Can copepods eliminate an existing diatom bloom?

Yes, the diatoms were eliminated from all of the test tanks that contained a serious bloom within one week of adding Algaebarn Ecopods. We also noticed that tanks with pre-existing populations of microcrustaceans never experienced a serious diatom bloom in the first place.

Every single tank that had the initial diatom bloom developed a layer of sludge on top of the sand after adding the pods which we presume was the processed waste left behind by the pods as they consumed the diatoms. That layer of sludge was easily removed and although the diatoms never returned, even after cleaning, the abrupt elimination of the diatoms (by the pods) often gave way to additional pests (cyano, chrysophytes, and algae).

Something else to consider about our test tanks specifically is that the considerable addition of pods caused a quick spike in nutrients which only fueled these residual pests. That sludge that was created and residual pests showing up was a clear indication that something changed with the addition of the pods and, in our case, elevated nutrients were part of it. 

Can copepods eliminate cyanobacteria?

Although pods are not known to consume cyano or chrysophytes directly, can the sheer competition for resources be enough to help outcompete these pests? 

The presence of copepods appeared to have no direct effect on existing cyanobacteria or chrysophytes and did not prevent residual blooms of these pests after a cleaning.   

With that in mind, the two tanks that were originally established early in phase 1 with an obviously diverse population of microorganisms and balanced biome were able to resist serious outbreaks of all the pests, even after the purposeful introduction of a pest slurry. Being proactive and adding pods early, before the lights are turned on, helps to ensure no one pest is allowed to dominate and will ultimately help to prevent serious outbreaks of photosynthetic pests in the long run. 

What about dinoflagellates? Can copepods eliminate dinos?

We didn't experience any particularly nasty dino outbreaks during our tests but science does tell us that certain copepods will eat certain types of dinoflagellates. Anecdotal evidence of this working is sprinkled throughout the hobby where those struggling with dinos saw a benefit from introducing pods. The success is likely very species-dependent; some dinoflagellates are toxic and others are not. What kind of dinoflagellates are you experiencing and what kind of pods do you have? Furthermore, will the abrupt elimination of dinoflagellates simply lead to an outbreak of cyanobacteria?

Do copepods have an effect on algae?

This depends on the type of algae really. Copepods won't eat macroalgae; hair algae is macroalgae. Pods focus on microalgae, smaller, unicellular algae that grow on sediments and are suspended in the water column.

In our test tanks, small tufts of hair algae survived the addition of pods. At the same time, tanks that had well-established microcrustaceans from the get-go never really experienced a threatening amount of hair algae growth. As we mentioned above, the takeaway with pods is their role in creating a diverse and balanced biome, and adding them early can help your tank be better prepared to handle photosynthetic pests should they arise. 

Yes, pods prey upon some photosynthetic pests which makes them a viable choice for eliminating some problems but prevention really is worth a pound of cure. What we witnessed with microcrustaceans during our experiment is all the proof we need. 

When one pest is eliminated, does another always take its place?

This is something we witnessed multiple times throughout the entire experiment. The elimination of one pest only gave way for another to come in and take its place.

The addition of pods eliminated the diatoms, but in many cases, the diatoms were replaced with algae, cyano, or chrysophytes. Think of it like a sort of reset in the biome where something like a large sledgehammer treatment kills the primary pest, only to make way for a new one to take over the newly available resources. The severity of these residual pests varied between the various test tanks but was almost a guarantee. 

The same thing would happen after a deep cleaning of the tanks. The biome balance is abruptly changed with the physical removal of pests and cleaning of the sand and rock surfaces. This often instigated some kind of residual pest bloom.   

Is live rock the best source of a diverse biome?

While the Gulf Rock tank produced the most diverse biome, it was actually the sterile control tank that produced the most balanced biome. Diversity proved to be important in the long-term defense of photosynthetic pests but without balance, that diversity proved to be a source of pests.

Something else we realized was that not all live rock is created equal. The Gulf Rock tank was far more diverse compared to the Indonesian Live Rock tank based on the AquaBiomics test scores and our own observations. The Gulf Rock tank was full of micro and meso-organisms including pods, tubeworms, snails, limpets, and even crabs while the Indonesian Rock didn't even appear to effectively carry microcrustaceans (pods) into the tank. 

Can copepods be eliminated from my tank by predators?

We saw something interesting in the "insta-tank" where we added corals as a means of establishing a biome. The corals carried red planaria flatworms into the tank which are known to prey upon small pods. We saw the population of planaria explode after adding the pods - seemingly double or triple the population compared to a relatively stable population of flatworms before adding the pods.

Did the flatworms eliminate the pods?  We don't know for certain and the likely story is yes, the flatworms ate the pods but probably didn't eliminate them completely within the test period.

There is something to be said about predators and the food chain. Things like flatworms or dragonets that target copepods as prey can disrupt the food chain and affect the population of pods in a reef tank. If these things exist in your tank, it could be a viable explanation for causing an imbalance in the biome. If your tank contains copepods predators, create a safe haven for pods like a refugium that is free of pod predators, or just know that manual addition of pods may be necessary to support a well-balanced biome.