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We get a lot of interesting questions here at UK Jellyfish. Questions range from ‘Can jellyfish be kept with sharks?’ to ‘If I chop my jellyfish in half will it become two? in effect two for the price of one?!’ The purpose of this page is to provide answers for beginner jellyfish keepers and those who may have been keeping them for a while.

Now I’m sure I’ve not answered all your questions here so if you’d like to ask anything at all give us an email at support@ukjellyfish.co.uk


Where should I set up my aquarium?

Your aquarium can be set up in a variety of locations. Most of our customers keep pet jellyfish at home, in the office or in a showroom.

Be sure to set up your jellyfish tank out of direct sunlight and near a power supply for the pumps and lights.

How many jellyfish can I fit into my tank?

This depends on which aquarium you have. As a general rule, we recommend that you have one jellyfish for every 5 litres of water in the tank.

For example a 45 litre aquarium can house 9 jellyfish (45 divided by 5 = 9).

What type of aquarium do I need for my jellyfish?

Jellyfish cannot live in a normal aquarium. They require aquariums that have no corners, a constant water flow and a protected outlet. Therefore jellyfish aquariums need to be made specifically for jellyfish. All our jellyfish tanks have been purpose built with jellyfish in mind.


How long will my jellyfish last without food?

Jellyfish can last up to three days without food. So if you were planning on a trip away this weekend your free to go!

How much food do I feed my jellyfish

Jellyfish feed continuously in the wild so we recommend you feed your jellyfish every day. The exact amount of food required to feed your jellyfish will depend on the type of food you have purchased. Each food order will come with a dosage information sheet.

What do jellyfish eat?

In the wild jellyfish feed on all sorts of creatures. Some of their favourite food includes ZooPlankton, PhytoPlankton, Brine shrimp and even other jellyfish!

We feed our jellyfish live brine shrimp for the best source of nutrition…


How long do jellyfish live?

Jellyfish are seasonal creatures. Their lifespan is up to 14 months.

How big will my jellyfish get?

Jellyfish grow into their surroundings. So depending on the size of your aquarium your jellyfish will grow in relation to the space around.

Moon jellyfish in an aquarium can grow up to 10 cm plus!

Can I keep my moon jellyfish with any other species?

No. Some would say you can keep moon jellyfish with blubber jellies but it is best to keep the two species separated.

Where do you source your jellyfish from?

All of our jellyfish are Captive Bred in our jellyfish laboratory. Captive Breeding means all of our jellyfish are disease free and have a longer life expectancy than jellyfish fished from the sea!

Always check the origin of your jellyfish!

Why is my jellyfish inside-out?

This is called inversion. Jellyfish are sensitive to water conditions, if the water is too hot or too cold the jellyfish will invert. To fix this bring the temperature back into their range, Lower temperature is best. Check the salinity and they should go back to normal.

Why can’t I just buy a regular aquarium for my jellyfish?

Jellyfish are very delicate. Introduced to a ‘normal’ aquarium you jellyfish would be cut to pieces by filters, corners, heaters etc. We sell custom made jellyfish tanks purpose built for jellyfish.

Postage & Packaging

How fast will my jellyfish be shipped?

All of our live jellyfish are shipped overnight. If you would like to specify a delivery date, please state this in the delivery notes box on the checkout page.

How are the jellyfish shipped?

Our jellyfish are double bagged, packaged in a polystyrene insulated box and surrounded by packaging. Jellyfish won’t last forever in their bags so they are sent for next day delivery.

Check out this video which guides you through our packaging process.

Watch Video


How often do I need to change the water in my tank?

We recommend a 20% water change every week to keep your tank looking crystal clear.

How do I mix salt water?

First you will need your RO water. You can pick this up from any local aquatic stores.

Then you will need your salt. Any aquarium grade salt will be fine for moon jellyfish.

Your salinity (Salt level) should be 25 grams per litre of water.

So for example you have the Medusa 45 Premium Package. This aquarium is 45 Litres.

25 grams of salt x 45 (Litres) = 1125 (Grams)

You will need 1.125 KG of salt for 45 Litres of water.

How do I test ammonia/nitrates?

Ammonia and nitrates can kill jellyfish so you need to keep them to a minimum. You can test your nitrates and ammonia using a simple marine test strip found in your local aquatics store.

Your ammonia and nitrates reading should read 0.

Ammonia and nitrates appear when you have been feeding your pet jellyfish too much or you haven’t cleaned the tank in a while.

If you need to get rid of ammonia or nitrate you need to do a partial water change every day until the levels drop back to zero.

How do I test Salinity?

To test salinity you can use a refractometer or hydrometer. These can be purchased at your local aquatic stores. These instruments give you a clear indication of how much salt is in your water.

Your water should be between 20-30ppt (Thats 20-30 grams of salt per litre).

How do I test the water temperature?

You can test your water temperature using a digital thermometer found in your local aquatics store. Your water should be between 17-21 degrees celsius.