Copepods in Aquarium – Are They Harmful?

Copepods are tiny white, brown, or cream-like crustaceans that live in water. This explains why they can also be found in aquariums. It is okay for fish to feed on them since they are rich in healthy fats. Copepods also feed on dead organic matter, which helps clean the tank.

Also known as roly-polies and pill bugs, copepods do not conflict with fish since they feed on algae and detritus. Copepods are natural tank cleaners. one copepod alone can clear up hundreds of thousands of diatoms.

While in their natural habitats, copepods feed on phytoplankton, which grows naturally on the substrate. These organisms also convert the sun’s energy into food to be used at higher trophic levels. It is critical to note that they do not necessarily need sunlight to survive. However, they need algae to supplement their diet.

Introducing copepods in an aquarium

Sometimes it may be necessary to introduce copepods in an aquarium, especially if the rate of diatomic build-up is quite high. It is a good idea to go for the commercial aqua-cultured types. They are usually well-nurtured and biologically tested to avoid parasitic types.

The best way to introduce copepods in an aquarium is at night when the fish cannot easily see them. Feeding the fish before the introduction is advisable to prevent them from eating the copepods.

It would be best to release the copepods as close to the substrate as possible to facilitate their proximity to the food source. Diatoms often build up on the tank’s surface and the substrate where fish feces drop, facilitating the formation.

Copepods in an aquarium
Copepods in an aquarium

There is no specific recommendation for the volume of copepods per tank, as the organisms multiply rapidly. Knowing the difference between copepods and other bugs like mites or springtails in an aquarium is also very important.

CausesWhat to do
Excessive food in the tankDo not overfeed the fish
Poor maintenancekeep the water clean. Keep the water filtered to remove dirt
Organic matterRemove impurities and extra food from the water
Lack of predatorsIntroduce filter feeders and larval fishes to eat them
Causes of copepods in aquarium + what to do

How to find them

If you are looking for tips on how to find them, a report submitted on copepods culture at the University of Florida suggests that; “Copepods for culture start-up can be collected from ponds, ditches and other standing water sources. This is done by quickly dipping a suitable container in water, particularly near submerged vegetation. After dipping, slowly pour 2/3 of the water into the container, and look at the remaining water for signs of the copepods. If copepods are present, quickly pour the contents into a clean container.”

The culture can be poured into the aquarium using a feeding tube that reaches the substrate. The copepods will easily settle on the substrate using this method. These organisms will begin reproducing as soon as they start feeding.

Characteristics of copepods in a tank

Copepods can sometimes naturally appear in a tank without the introduction. In most cases, they are carried in live sand and rocks without being noticed. They are most likely attached to the sand or rocks as larvae or eggs, which are difficult to see.

Some adult copepods might be too tiny to spot with ease. However, the most practical way to spot them is to turn off the pump at night, so there is no bubbling. Then shine a spotlight through the glass. If copepods are present, they will most likely swim toward the light. This way, you will know whether you have them in your tank.

Larger versions of copepods are known as amphipods. These can consume a variety of wastes, including fish waste. They also eat most of the waste that forms and sticks onto surfaces and substrates.

Note that even the larger copepods are not really large and can squeeze into tiny spaces and reach for the waste in those spaces. Here is a video explaining what copepods eat;

What copepods eat

Are copepods good or bad?

Some aquarium owners view copepods as pests, yet they are not. These tiny organisms help clean the aquarium and provide an extra food source for the fish. Their feed on algae makes them even more nutritious and valuable for the fish.

Imagine copepods as workers providing free labor and still contributing to ensuring you and your family get enough food to sustain you. Simply put, their benefits are way more than can be imagined. However, you must learn to eliminate copepods in a fish tank if you feel they are too much.

Eliminating copepods from the aquarium is easier than it may seem. Some of the steps include:

1. Siphoning

Copepods are generally attracted to light. Shining a spotlight on the tank in the dark will attract them, and they will swim toward the light source. They can be easily siphoned or sucked out of the tank using a suction pump and a PVC pipe.

2. Avoid overfeeding the fish

Less feeding of the fish reduces the volume of waste disposed of daily. A scarcity of food sources translates to a reduction in copepods within the tank. Less food will stop their numbers from growing while the fish feed on them.

3. Introducing predators

Certain freshwater fish species, especially the smaller ones like guppies, mollies, and tetras, are excellent copepod eaters. They can easily spot these tiny organisms that may be difficult for bigger fish to spot.

Even though some may view them as invaders and even refer to them as fish lice, copepods are an excellent addition to an aquarium. They clean your aquarium and supplement the fish diet in any setup, which is just part of the benefits of Live Copepods in a fish tank.

Copepods in a reef and shrimp tanks

Copepods are critical in all reef tanks for various ecological reasons. First, these organisms act as grazers, feeding on microscopic microalgae. The second function is that they act as scavengers, where they feed on detritus. Finally, they act as food for certain zooplankton.

They provide the coral with an excellent food source, particularly supplementing the fatty acids they extract from the microalgae. Copepods can also help clean the microalgae off the reefs, allowing the coral to breathe easily.

Additionally, copepods also help maintain the water quality of coral. Determining if the water quality is not fair to coral is difficult. Therefore, a natural means of maintaining the water quality might do more good for the coral. It is advisable to have as many copepods as possible in a reef tank to improve the health of the coral.

Shrimps are not known to go after copepods. It is also apparent that shrimps produce waste and are likely to have grime in their tanks. It may not be uncommon to spot large colonies of copepods in a shrimp tank due to the availability of food sources alongside the lack of a natural predator.

The presence of copepods in a shrimp tank must not be a cause for alarm as they are rarely harmful to shrimps.

If you are not interested in having copepods in a shrimp tank, it may be advisable to introduce more friendly fish that will not feed on the shrimps but can eat the copepods. The introduction may be a temporary remedy, and the fish can be returned to their tanks after completing their purpose.

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