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Should You Be Worried About Water Fleas In Your Aquarium?

With the recent surge in beginners to fish keeping and taking care of aquariums, we have noticed a steady increase in the number of people reaching out about having water fleas in their aquarium.

We really have noticed a wide range of questions being asked about water fleas too with some people being worried about the fleas in their aquarium to others asking about the best type of fleas to intentionally add to their aquarium for live feeding their fish.

Due to seeing such a large number of people asking such a wide range of questions, we wanted to publish our own, dedicated article on having water fleas in your aquarium to try and help as many of our readers as possible.

It is understandable for beginners to be worried about having water fleas but there are over 450 different types of water flea with the majority of them being harmless with most types of the daphnia water flea internationally being added to many aquariums due to being such an excellent source of food for smaller fish.

Still, we see people reaching out month after month with a bunch of questions about water fleas and wanted to answer them all in this article.

We have added our table of contents below to allow you to quickly and easily skip to specific sections of the article to get to the information that you need without having to skim the full article.

Should You Be Worried About Water Fleas In Your Aquarium?

Although a small number of water fleas can harm smaller fish and fry, the majority of water fleas will usually end up being a food source for smaller fish rather than the fleas eating your fish.

Although there is usually nothing to worry about when it comes to having water fleas in your tank, some people don’t like them due to it detracting from the overall look of the tank.

The second most popular option for live feeding fish is actually the daphnia water flea with a huge number of fish keepers all around the world often intentionally adding them to their tanks due to being such a great source of fish food.

There are also a number of other types of water flea that people intentionally add to their aquarium as a source of fish food too but daphnia are by far the most popular option.

If you are intentionally trying to breed fish then the water flea in your tank can present a very real risk to the fry while they are still small.

Some water flea species will also eat or damage fish eggs too making it harder to get a breeding tank working correctly so you may need to remove the water flea from the tank as quickly as possible.

Are Water Fleas Bad For My Aquarium?

The majority of the types of water fleas are not necessarily bad for your aquarium and can sometimes actually help to keep the algae buildup under control.

There are over 450 species of water flea and only a fraction of them present any real risk to your aquarium and even then it is usually only to smaller fish.

As we mentioned above, fish fry are particularly vulnerable to some types of water flea with the eggs also being vulnerable too.

This is why we would recommend that you do your best to get rid of any water flea infestations in any of your aquariums that you use for breeding fish as quickly as possible.

Although it is not necessarily a bad thing for your aquarium, some people do take a large amount of pride in their aquariums and use them as a centrepiece for their homes to show off to guests.

Water fleas can be considered bad for this type of show aquarium as it can take away from the overall look and feel of the aquarium with most people choosing to remove the fleas as quickly as possible.

How Do I Get Rid Of Water Fleas In My Fish Tank?

There are a number of ways that you are able to get rid of fleas in your aquarium with the two most popular methods being a full water change or to add fish to the aquarium that will eat the water fleas.

Although there are some chemical products on the market that are marketed as a quick and easy way to rid your aquarium of water fleas, they tend not to work and are usually a total waste of money.

Changing the water in your fish tank can be problematic due to water fleas often still being in the substrate of your tanks so once you refill it with new water, their population can quickly and easily grow again.

Some people actually go as far as removing the majority of the accessories from their aquarium to rid themselves of some species of water flea due to them being so resilient.

This is why our preferred method is to just add a fish that will actively eat water fleas in large quantities each day.

Depending on the size of your tank and the number of fish that you add to each the water fleas, it can take as little as a week and as long as a month for all of the water fleas in the tank to be transformed from pests to food.

The majority of fish in the Poecilia genus are excellent options for this with guppies being one of the more popular water flea eaters out there.

What Aquarium Fish Eat Water Fleas?

The majority of small and medium aquarium fish will happily eat large amounts of water fleas in their aquarium and can easily remove the majority of the water flea population in their tank in as little as a week.

Some of the more popular fish that will eat large amounts of water flea include guppies, mollies, betta fish, and regular goldfish.

In our opinion, guppies are one of the better options due to them being easy to care for and being able to be added to a huge range of aquariums without causing any problems.

Although betta fish do eat a large number of water fleas in their aquarium, they tend to be a poor choice for communal tanks due to issues with aggression in the fish making guppies or mollies a better option.

The majority of fish that are under six inches will happily put the effort into catch and eat water fleas like daphnia though.

Just some enjoy the chase more than others and although larger fish may chase daphnia every now and then, the larger the fish is, the less likely it is to actively go looking for daphnia.

How Do Water Fleas Get Into My Aquarium?

Water fleas can get into your aquarium in a number of ways with new fish or plants usually being the most common ways that water fleas can get into your tank.

Some forms of substrate can also have water flea eggs in them too but this does tend to be rare. A large number of people will also intentionally add water fleas to their aquarium as a food source for their fish.

If you are intentionally trying to keep your aquarium free from water fleas due to it being a breeding tank and having a large number of eggs and/or fry in it then we would highly recommend that you start to quarantine any potential new additions to the tank.

Although this may sound strange, holding any new fish, plants, substrate or rocks in a separate tank for a few days to see if water fleas start to emerge is definitely worth it.

This really is worth it as water fleas can cause havoc with eggs and fry if you are intentionally trying to breed fish.

Experienced breeders will usually already be aware of this but there are a large number of people just getting into breeding fish who may not know how many problems water fleas can cause in a nursery tank.


That brings our article going over having water fleas in your aquarium to an end. We hope that we have been able to help you understand why there are water fleas in your aquarium, how they got there, how you can get rid of them, and the potential risks of water fleas. That said though, for the majority of our readers, the risk of water fleas in your aquarium really is minimal with there usually being no need to worry about them.