What is the Nitrogen Cycle and Why Is It Necessary for My Aquarium?
A jellyfish tank is essentially a marine aquarium that will house animals—our jellyfish. In creating a closed, isolated, and healthy environment, it’s essential to have a mature biological filter where the nitrogen cycle can take place.
Why Is It Needed?
All animals produce waste. Jellyfish do not excrete solids but instead release waste products that dissolve in the water. In addition to jellyfish excretions, there are wastes from decomposing food.
These waste products—mainly ammonia (NH₃)—are invisible but present. They must be eliminated because over time, they turn the water toxic, and jellyfish cannot survive in it.
While you could perform daily water changes to remove ammonia, this is not practical. The best solution is to have a filter that transforms ammonia into less toxic molecules. That’s why it’s so important to have a healthy, mature biological filter.
Who Carries Out the Nitrogen Cycle?
Nitrites (NO₂⁻) → Nitrates (NO₃⁻) → less toxic
To prevent nitrate buildup, perform a partial water change about every 10 days.
How Do I Start the Cycle?
Set up your jellyfish tank with saltwater, adjusted to the right salinity and temperature.
Place the bio-balls or filter media into their compartment.
At this stage, the water may look ready—but it’s not a safe habitat yet. If jellyfish are added now, they may not survive the week.
- How to Start the Biological Cycle:
The filter media needs to be colonized by nitrifying bacteria. These need a food source—in this case, ammonia. Once ammonia is present, the bacteria begin to grow. You can do this in several ways: - Method 1: Natural Cycling
Add a bit of food and allow it to rot and produce ammonia.
Wait 4–6 weeks for bacteria to naturally colonize the filter and complete the cycle.
Method 2: Food + Bacteria Starter
Add food to create ammonia.
Inoculate with bacteria from commercial products like Stability by SEACHEM.
Speeds up the process: ~3–4 weeks.
Method 3: Ammonium Salts + Bacteria
Add ammonium salts provided by MEDUSEA.
Inoculate with Stability or FRIZZYME bacteria.
Fastest option: ~2–3 weeks. - What to Expect During Cycling
After adding the ammonia source:
You’ll see an ammonia spike, followed by a drop.
Then nitrites will rise as bacteria convert ammonia.
When both ammonia and nitrites reach zero, all nitrogen is now in the form of nitrates.
This usually takes 3–4 weeks. At that point, do a 20% water change to reduce excess nitrates.
Now your aquarium is ready for jellyfish!
Important Notes
Your biological filter is a living system and must be cared for:
Do not pour water with different salinity directly on the bio-balls. This could cause osmotic shock and kill the bacteria.
Ensure bacteria have a constant source of waste (food for them).
If no animals are in the tank temporarily, add small amounts of food periodically so it decays into ammonia.
This way, your aquarium will always be ready for jellyfish or other marine animals.
Now your tank is truly ready to welcome jellyfish!
Important Notes
Your biological filter is a living system and must be cared for:
Do not pour water with different salinity directly on the bio-balls. This could cause osmotic shock and kill the bacteria.
Ensure bacteria have a constant source of waste (food for them).
If no animals are in the tank temporarily, add small amounts of food periodically so it decays into ammonia.
This way, your aquarium will always be ready for jellyfish or other marine animals.