What do Healthy Jellyfish Look Like?

Jellyfish are strange and very foreign creatures. They’re often compared to alien spacecraft, and deservingly so. Unfortunately, these enigmatic creatures don’t have brains or mouths to tell us when they’re upset. As jellyfish guardians, we have to be able to tell the difference between a healthy jellyfish and a sick one.

For this post, we’re going to be using the Moon Jellyfish for all of our examples. Other species may vary slightly, but should be very similar.

What does a healthy jellyfish look like?

A healthy jellyfish should have an even, round bell. Their bodies should be fairly thick, and smooth. A happy moon Jellyfish will have hundreds of tiny fringe tentacles at the edge of the bell, and four mouth arms in the center. It should pulse once every few seconds.


In the above photo, notice how there are tons of long, hair like tentacles at the edge of the bell. These “fringe tentacles” are a good indicator of health. They should be long, relaxed and flow smoothly as the jellyfish pulses. They do tend to retract these while eating, so don’t be alarmed if they temporarily disappear!

Also notice the width of the bell. This is exactly how wide a healthy Moon Jelly should be. Thinner ones are less nourished, and may not be getting enough nutrition. IMG_1013.jpg

Note that the bells are round and very smooth. The jellies maintain a sort of half circle form. They aren’t thin like plates, but also aren’t balled up into a sphere. Both extremes are bad signs.

We hope this post can be used as a reference guide for your own jellies at home. Stay tuned, as our next post will be on common jellyfish ills and ails.

At the Jellyfish warehouse, we put the highest level of effort and research to create happy and healthy jellyfish for the home aquarium. You can purchase your own here: Jellyfish Warehouse

How to Lower Nitrates in a Jellyfish Aquarium

Nitrates are likely the most disliked molecule in the aquarium world. They’re a result of food and waste in your aquarium. But unlike ammonia and nitrites, nitrates won’t go away on their own. We’ll explore the reasons why nitrates are undesirable and some easy ways to get rid of them! 

What are Nitrates and Why are They bad?
Nitrates are the by product of jellyfish waste (jelly poop!) and uneaten food being broken down. Jellyfish will release highly toxic ammonia, which is quickly broken down into nitrites and eventually nitrates by friendly bacteria in your aquarium. But under normal circumstances, these friendly bacteria can’t break down nitrates. More on that below.

These nitrates will build up over time, which can eventually impact your jellyfish. In low levels, nitrates won’t bother your jellies. But as those nitrates creep up, it will begin to impact your jellies. Based on your nitrate readings, these are the results you can expect:

0-10 ppm nitrates: Happy jellies! 

10-20 ppm nitrates: Happy jellies but slower growth. 

30-40 ppm nitrates: Significantly stunted growth, jellies may stop growing all together. 

50+ ppm nitrates: Past this point, your jellies may actually start shrinking in size. 

How do I Measure Nitrates? 

Nitrates can be quickly measured with a nitrate test kit. We highly recommend the Nitrate test kits by RedSea. These kits are renowned for their accuracy and reliability. We highly recommend stealing clear of test strips or other all in one type tests, as these tend to be unreliable and inaccurate. 
When jellyfish are exposed to high levels of nitrates (40ppm+) for extended periods of time, it can shorten their lifespan. So it’s best to keep those levels low! If you have high nitrates, it’s nothing to panic about! Let’s look at some ways to lower nitrates and keep them low.

  1. Water Changes: This is the oldest method in the book, and the most reliable. Nothing beats a reliable and consistent water change schedule! You should try to change around 20% of the water in your jellyfish tank every 1-2 weeks. A regular water change schedule should keep your nitrates very low on its own. If your nitrates are already high, you can do larger water changes to cut them down. We recommend doing 50% water changes every 2 days until your nitrates are in a good range. Larger water changes could be too stressful to your jellies so stick to 50% every two days.
  2. Add some Matrix media by Seachem: Matrix is a highly porous filter media produced by the company Seachem. It has an incredible amount of surface area, which allows all those friendly bacteria to colonize. The center of Matrix is dense, meaning it can house bacteria that don’t like oxygen (anaerobic bacteria). These new bacteria can effectively reduce nitrates. Packets of Matrix fit perfectly in the outer compartment of your Orbit tank!
  3. Lower your feeding: We all love to feed our jellies and see them grow. But sometimes we feed them too much. If you’re feeding JellyFuel, your jellies only need a few pellets of food each. 
  4. Remove uneaten food: Food that isn’t consumed just turns into nitrates, without being useful to your jellyfish. Try using a feeding pipette to blow extra food around. The jellies may continue to eat. Any more food that settles to the bottom can be removed. 
  5. Don’t add unnecessary bacterial supplements: some companies will try to get you to add bacteria-in-a-bottle type products on a regular basis. These can do more harm than good, however. Bacteria need food to survive. So only so many bacteria can live in your tank, before they start to starve. Continuously adding bacteria means many of them will die, and just end up producing more nitrates. It’s a good idea to add some beneficial bacteria when you start your tank. But once they’ve seeded your tank, there’s usually no need to add more. 

Conclusion: Nitrates aren’t all that bad, but it’s good practice to keep them lower than 20 ppm. Doing so will ensure your jellies are healthy, growing and love long lives. Water changes are the easiest and most effective for removing nitrates. Feeding sparingly goes a long way! 

You can get your own jellyfish and jellyfish aquarium at the Jellyfish Warehouse. We’re always happy to answer any questions you have. Feel free to email us at any time: Email us!