Nitrogen Cycle In Aquarium

Aquarium Nitrogen Cycle (The Complete How-To Guide)

Have you ever wondered why experienced aquarists, after buying a new aquarium, leave it for a few weeks with only decaying dead shrimp or fish food and not a single live fish swimming around? Most likely, they’re probably waiting for their tank to cycle so it would be safe enough for the fish, shrimp, and other pets to live in.

The nitrogen cycle is the single most important factor in the aquarium hobby and it cannot be ignored!

You must learn the Nitrogen Cycle if you want to keep tropical fish. Your aquarium must cycle before you can house fish, if your tank doesn’t go through the Nitrogen Cycle your fish will die. NOT GOOD!

What Exactly Is The Nitrogen Cycle?

Fish, shrimp, snails, and other pets you add to your tank all give off some kind of waste. This waste turns into ammonia, which is highly toxic to any tank inhabitant except for plants and algae. Fortunately, there are beneficial bacteria that actually convert ammonia into a less toxic form—nitrite. In most cases, however, nitrite is still highly toxic and could still be fatal to fish and invertebrates.

Fortunately, another group of beneficial bacteria converts nitrite to nitrate, which is tolerated by fish and invertebrates in relatively large amounts compared to ammonia and nitrite. These bacteria take time to grow; therefore, new aquariums that are immediately stocked with fish often experience the “new tank syndrome,” which leads to quick fish and invertebrate deaths. The nitrogen cycle immediately starts when a source of ammonia is present, which we’ll talk about further when we discuss the process of cycling your tank.

How Do I Cycle My Aquarium Fast?

To date, there are two main ways of cycling your tank: traditional cycling and fishless cycling. The traditional method of cycling involves adding a fish to your tank, thereby jump-starting the beneficial bacterial colonies that convert the dangerous waste produced by the fish into less toxic form. Unfortunately, this process often kills or permanently damages the newly added fish due to exposure to toxic ammonia.

The fishless method of cycling which is considered the faster and is definitely the more humane way of cycling a tank, simply because you’re not sacrificing a pet in the process. You simply need an ammonia source to jump-start the development of beneficial bacteria colonies.

The product that we use and recommend is Fluval Cycle 

How To Do A Fishless Cycle

Once you have picked up a bottle of pure ammonia, you are ready to get started with your fishless cycle. The process is simple but it may require a few runs over in order to understand properly. We recommend bookmarking this page for future reference.

Fishless Cycle: Step-By-Step Process 

1. Set up your aquarium – Fill it up with water and set-up your filters, rocks, substrate, plants, etc.

2. Add a dechlorinator to your aquarium – Chlorine kills bacteria, including the ones we’re trying to help grow colonies in the tank.

If you don’t already have a decholorinator, we highly recommend that you stick with Seachem Prime Water Conditioner

3. Keep the temperature stable (77°F-86°F) – The beneficial bacterial colonies grow quickly in this range, so keep it stable.

Keep the aquarium lights off if you don’t have any live plants. Algae spreads quickly under heavy light and can quickly cover your entire tank.

4. Turn on your filters and aerators – Anything that agitates the water surface helps oxygenate your tank and therefore encourages the beneficial bacteria to grow.

5. Add your ammonia source – Add about 4 ppm of ammonia (You’ll need an ammonia test kit for this).

6. Find stuff from an old aquarium and add them to your new aquarium – From rocks to tacky aquarium decorations, beneficial bacteria colonies aren’t picky. Find stuff from an established tank to help seed beneficial bacterial colonies into your tank and help it cycle faster.

7. Wait and see – Keep checking your ammonia every few days; it’ll eventually start to drop. When it goes down to 1 ppm, dose it back to 4 ppm so as not to starve the beneficial bacteria. Do this about 1-2 more times, and then start testing for nitrite. Keep dosing ammonia to push ammonia levels back to 4 ppm, and keep an eye on nitrite levels. If the nitrite levels start to fall, then you’re on your way to the end of the cycle!

9. Water change – After a while, nitrites should drop down to zero. Nitrates should be really high at this point. You’ll want to remove about half of your tank water to remove a lot of nitrates.

10. Add fish! – When both ammonia and nitrites are zero, you can finally add fish as long as your nitrates stay at an acceptable level (For marine tanks, that’s about 0-20 ppm.

For freshwater tanks, that’s about 10 ppm-40 ppm.). If the nitrates are too high, do a 50% water change.

Remember never to do a 100% water change, as this may cause the nitrogen cycle to start all over again!

That’s it! After days or weeks of waiting, your aquarium is finally ready for its first fish!

Cycling typically takes about a month to complete, possibly faster with the addition of stuff from established tanks.

Remember to stock slowly to give the beneficial bacterial colonies enough time to grow and adapt to the increased bioload. Test and change your water regularly and you should have a thriving tank in no time.

The test kit that we have used for years is the API Freshwater Master Kit. It’s affordable, but most importantly, it’s reliable.


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