Freshwater Jellyfish – Care, Diet, Life Cycle, Breeding

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When we hear the word jellyfish, the first thing that comes into our mind is a gelatinous, transparent creature that lives in the ocean, which should be avoided.

Not many know that there is a jellyfish, which lives in freshwater lakes. The Craspedacusta sowerbyi, freshwater jellyfish can be found all over the world in lakes and ponds.

Because their size is relative small, and their body is transparent, these freshwater jellyfish go unnoticed and many still believe that there are no medusas that live in freshwater.

Terry L. Peard, Ph.D. dedicated its life to study these freshwater jellyfish and to build a database with the locations where these small creatures can be found.

In this article, you will find information about the breeding, life cycle, diet, water requirements of freshwater jellyfish and other interesting things.

What is the Size of Freshwater Jellyfish?

As mentioned before, freshwater jellyfish are really small. In their medusa (adult) form, this jellyfish reaches up to 0.75 inches (1.9 cm) in diameter, which is the size of a penny.

So, one creature will most likely swim around unnoticed, while even a bigger swarm will be really hard to detect, due to their fully transparent body.

What is the Lifecycle of Freshwater Jellyfish?

Freshwater jellyfish have similar life cycle as saltwater jellyfish.

They start their life as a zygote, which is developed from the egg and sperm of adult medusa.

The zygote becomes a planula (larva), which floats in the water until they attach to a hard surface such as rocks or plant leaves.

Eventually the larva develops into a polyp, which reproduces asexually by so-called budding. The polyp is budding off ephyras (immature medusas), which eventually turn into adult medusa.

The adult medusas will eventually reproduce (sexual reproduction) as well, by releasing eggs and sperms, and the whole process starts again.

So to recap, here are the life stages of a jellyfish:

  1. Zygote
  2. Planula (larva)
  3. Polyp
  4. Budding polyp
  5. Ephyra
  6. Medusa (adult)

Do Freshwater Jellyfish Sting?

Just like other jellyfish, freshwater jellyfish have stinging cells and they sting. They use their stinging cells to catch paralyze the prey and to feed on them.

They might be able to sting and paralyze smaller fish, however they are harmless to humans, because their stinging cells can’t penetrate the skin of an adult person.

That said, it is better not to touch them, because depending on the persons sensitivity level, the contact with a medusa can cause skin irritation and itching.

How to Catch Freshwater Jellyfish?

Never catch a jellyfish with your bare hands. You can use a net or a small plastic container to extract the jellyfish from the water.

Can You Keep Freshwater Jellyfish in Aquarium?

Yes, freshwater jellyfish can be kept in aquariums, though it might be difficult.

It is much harder to maintain a freshwater jellyfish aquarium than one with fish.

Jellyfish don’t like strong water flow, so a strong aquarium pump will harm them. Even a sponge filter can stuck the jellyfish onto the sponge.

I would not recommend keeping jellyfish together with other fish, because their stinging cells can easily kill the smaller tank mates.

If you want to setup a jellyfish aquarium, you should use at least a 20 gallon tank, with deep substrate and a water pump that slowly circulates the water.

Also make sure, that the water parameters are stable and there is plenty of food in the tank.

What do Freshwater Jellyfish Eat?

Jellyfish can’t eat just normal fish food, they will need live food. They prefer to eat brine shrimp, daphnia or other small water creatures.

Occasionally jellyfish will also eat smaller fish, such as guppy fry or other baby fish.

What are the Best Water Parameters for Freshwater Jellyfish?

The best water temperature for freshwater jellyfish is in the 68-77 °F (20-25 °C) range.

The pH of the water should be neutral, having a 6.5-7 pH range.

Can You Breed Freshwater Jellyfish in Aquarium?

While it is very difficult to keep the jellyfish alive in a home aquarium environment, their reproduction is even harder.

I’ve never heard someone to be able to breed freshwater jellyfish at home.

How to Tell if a Jellyfish is Male or Female?

Until full maturity, it is impossible to sex jellyfish. When they are ready to breed, there are some slight visible differences between males and females.

Do Fish Eat Freshwater Jellyfish?

Usually fish will avoid eating jellyfish, however crayfish or turtles will consume them.

Can You Keep Jellyfish in a Fish Pond?

In some areas, freshwater jellyfish naturally occur in fish ponds and for some pond owners, this might be a very unpleasant surprise.

Freshwater jellyfish will not harm bigger fish, but can paralyze smaller fish fry.

Because the lifespan of adult jellyfish are relatively short, they won’t cause too many problems in a natural pond.

In ponds, where water is filtered through a water pump, freshwater jellyfish might not be able to survive due to strong water flow.

What is the Lifespan of Freshwater Jellyfish?

The lifespan of freshwater jellyfish is not known exactly. One thing however is certain, that adult medusas will die off after they mate.

How much do Freshwater Jellyfish Weigh?

Freshwater jellyfish weigh between 3 to 5 grams (0.11 to 0.18 ounces), so they are not just very tiny but also very lightweight.

Wrapping Up

I really hope, that this article will help many people to learn about freshwater jellyfish.

Please leave a comment below if you have ever seen a freshwater jelly fish and tell us where you spotted it.

Author Image Fabian
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.
Questions and Answers
Marcus E Baxley November 28, 2020 Reply

Lower Crooked Lake in Delton, Michigan. I’ve seen these jelly fish on and off for 20 years.

    Stephan Corley December 12, 2020 Reply

    I live in Ohio,just a couple miles from Lake Erie coast line near Lorain.
    I learned of these critters only a couple years ago.Im new at aquariums .But,it seems I have a knack for it.Now,I find Im wanting a freshwayer jellyfish.

      Great info man. About the ph and temp. I was looting for the info. I am going to try to keep these. But i want to set up a stable environment with a little circlation in the water and then try to get a couple.

    We found them at crooked lake probably 50 years ago. We got our name in the newspaper. I wish I could read the artical again.

          Harriman Pond, Dedham Maine spotted 3 weeks ago (9/17/22) and then again last week. I found several very large blooms of them. When I went back to get my phone for pics the blooms had broken up quite a bit.

    Joseph Duchesne July 4, 2022 Reply

    Androscoggin River, Errol,, at 7 islands. Lots of them stuck to the rocks.

    Starry Jiang August 3, 2023 Reply

    You are lucky!I live in China and it is difficult to watch these lovely animals here=(

    Vicki Steffen July 18, 2022 Reply

    Audra we also have these special creatures in our Indiana pond. Usually the 3rd week of July. I’ve been checking several times a day. Love to watch them. This hopefully will be the 6 th year for them.

    Robert Schwalm August 27, 2022 Reply

    Found in my pond in Pine Grove Pennsylvania. Our pond was put in in 1980 and this is the first time we seen them. Never knew they existed.

August 2021

Spotted these jelly fish while fishing on the recreational Welland Canal in Welland ON.

Zady Kitty August 25, 2021 Reply

We have seen fresh water jelly fish on many occasions in Lake Saint Helen, in Saint Helen, Mi. Roscommon County.

Chris Berlew August 27, 2021 Reply

August 2021 in the Lily Pond, Deer Isle, Maine. I’ve been swimming there in August for at least 30 years and this is the first time I’ve seen them. This year I’ve passed through at least three conspicuous swarms on every swim.

    Katherine Lawson August 4, 2022 Reply

    Andrea Kunkel posted on Facebook today that she saw some in there yesterday. I hope I get to see some too!

    They are there again in the Lily Pond, Deer Isle this year. They usually appear in August when the water is warmest. There were many swarms of them today when I swam.

Gavin Fregona September 4, 2021 Reply

I saw 3 fresh water jelly fish yesterday while snorkelling in Lake Erie near Selkirk Provincial Park. I have some GoPro pics of them if anyone is interested.

    My husband and I saw several hundred of them today in pine hill lake, Jackson county Michigan. We have lived here and used these lakes since 1970 and have never seen them before. Fascinating.

      They have been seen at lake of the ozarks mo for about 30 years. My fiancee and fishing buddy brought one home in a water bottle. I was shocked, upon searching at that time on internet government claimed they were not jellyfish but very distant correlation species which came from asia.
      Now they say they came from china and are jellyfish. Heavy infiltration east coast to midwest by map.
      One could assume it came here via shipment on east coast frieght at port.

Larry Beard September 7, 2021 Reply

While fishing in the chain of lakes near Langston. Michigan on labor day.we discovered thousands of these jelly fish in four of the five lakes

Theresa Ukele September 7, 2021 Reply

Hi, my name is Theresa. I brought my grandsons down 2 Timberline Lake in Bonne Terre, MO this past Labor Day wknd. They we swimming yesterday 8-6-21
my grandson Braeden spotted the small freshwater jellyfish. We had NO idea they were in this lake. My mom & dad live up the road, around the corner on a different lake, both are spring fed. I have been learning as much as I can.
Wonders never cease to amaze…

Hello I’m Amanda
I have seen freshwater jellyfish in the Chinook Pond in Staunton Indiana, today 09-08-2021

Jamie Replogle September 28, 2021 Reply

9/27/2021 North Lake Pleasant Coldwater, Michigan. The entire lake was full! Amazing creatures!

My husband and I spotted a bunch in Joe perry lake, Bon Echo provincial park, ON. Oct. 2nd, 2021

Melissa Bontrager October 5, 2021 Reply

We see them every few years in Lake Wahbememe (White Pigeon, MI), usually in August. It’s so exciting to see fun creatures reappear!

    Lonnie.R.Wilson September 10, 2022 Reply

    we having freshwater jellyfish in our pond in Connecticut Chester Connecticut

    Laurie Preece January 24, 2023 Reply

    This is Amazing! I’m from Michigan, Love it and there Beautiful Waters! The 1st time I’ve heard of these fresh water jellyfish was while reading a plaque about Rose Lake in Hocking Hills, Lorain OH on 1/21/22I will be on the lookout for these lil wonders in the waters! Thanks 🐟🐡

Loon Lake in Oscoda County Michigan, Thur. Sept. 30, 2021 – Swarms of fresh water jelly fish. Note the lake had gone down a foot from the same time the previous year.

Mike Haynes October 24, 2021 Reply

When I was a kid I used to see them go over a small spillway close to our house in central Florida. Nobody ever believed me.

Tom Zimmerman October 26, 2021 Reply

I just pulled my pontoon off Lake Nockamixon for the season, there was a jellyfish (large about 4-5″in diameter) stuck to the one pontoon. Other people there had asked the park rangers about them and were told they are there because of the clean water.

Thank you for the great article
I found a 1/4” jellyfish in a nearby creek in Katy, Texas. For one FW Jellyfish, what size of tank do you recommend?

Mike Ryan April 7, 2022 Reply

Are you familiar with the old Quarry in Hallam Township, York County? I hear someone say that it also has the freshwater jellies in it. I’m thinking he may have meant the Quarry in Lancaster.

Vicki Steffen July 18, 2022 Reply

We are patiently awaiting their arrival. This will be the 6 th year that they’ve arrived in our private pond. I recently retired from a school and took these in for show and tell for 5 years. I scoop them up with a mason jar. Kids have really enjoyed them. Will let you know when their up. Also our local paper did an article when they first appeared in 2017.

Karen ritchie July 23, 2022 Reply

We just found some in our pond in ky. Will they survive our winter

Joseph Fusco August 14, 2022 Reply

Little Pea Porridge Pond – Madison, NH – sighting 8:45 am on 8/14/22, at least a few dozen size from a dime to a quarter.

We have thousand of these fresh water jelly fish in our 4 acre pond in Hallstead, Pa. I noticed them 4 years ago and every Aug. they’re back. My dogs swim right through all of them.

Nelson Metz August 26, 2022 Reply

I saw freshwater jellyfish at Devil’s Kitchen Lake in Southern Illinois. I had never seen them before and was amazed.

Jocelyn Malamy September 12, 2022 Reply

Has anyone seen them this year? I am interested in collecting and would appreciate hearing about locations. I can be reached at vianne87 on yahoo . Thank you!

    Dugger Indiana red Budd Lake Green Sullivan State Forest Indiana southern Indiana thousands and thousands of them in this one pond no fish to be found just jellyfish I caught one and brought it home in a jar and put two minnows in it to see what would happen On this date 9/17/22

      Jocelyn Malamy September 26, 2022 Reply

      Thanks Robert. This is tremendously exciting news for me! I could get there next weekend. Any idea if they’re still there? Feel free to email me privately at yahoo. vianne87.

I saw a jellyfish for the first time in Lewis Smith Lake, Jasper, Alabama this past Sunday, September 18, 2022.

Lake Eileen, Gilmanton NH, just saw them there on a fishing trip this week, first time i’ve ever seen them. Might try to keep some in a fish tank

Judy Heininger October 15, 2022 Reply

I just saw the freshwater jellyfish for the first time in my life, I didn’t know they exist!! I am a saltwater sailor, so am accustomed to seeing them in the ocean. These little guys (or gals) caught my eye as I drifted around in a kayak, chatting with a friend who was in her kayak. We were on Pea Porridge Pond in Madison, New Hampshire (the big pond, not Middle or Little). Thanks so much for your website, very exciting!

Julie Krisak October 21, 2022 Reply

We saw them in Randlett Pond in Meredith. They have been here since mid summer, the pond was very warm. There were tons of them today, October 21sr.

I used to live in the Ozarks, near Kimberling City, MO and saw them years ago in a spring-fed cove, upriver from Table Rock Dam. I couldn’t believe my eyes and asked my late sister who had a degree in environmental interpretation if they actually existed. She said, “Yes! They tend to live in places with clean water”. Sighting them was a real high point during my time living there during the 1980’s and 1990’s.

    Starry Jiang August 3, 2023 Reply

    It is right!I am a Chinese and in my hometown,Jiangxi,they are found in a reservoir.(Althogh it is another kind of freshwater jellyfish and actually it’s endangered=(

saw them in a lake in Deltona, Florida. 1989 +-. lots of them like snow in the water. didn’t think it was real.

Leanna Webb July 1, 2023 Reply

I have thousands of these in our private pond in Florida. This is the first time we have had them in our pond. I suspect they were introduced to the pond via live feeder fish I have recently ordered. They are quite beautiful to watch as they swim. We scooped a few up in a bucket and placed in a clear glass tall boy. It’s really hot here so I am unsure how long they will survive. Guess we will soon see.

Stephen Eli House August 2, 2023 Reply

Found these by the thousands in a private pond in Paulding County Georgia. Took some home and have kept alive for a few days in my Beta tank

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