The nitrogen cycle is a crucial part of fish keeping. In the aquarium hobby we call what we’re going to be talking about “parameters” or “levels”. We’ll be focusing on 3/6 of the main parameters: ammonia, nitrite and nitrate. These are all harmful.

Ammonia is the most toxic, nitrite being less, and nitrate being the least toxic, but you still want it under 20 parts per million.

Cycling your tank is basically just letting bacteria colonies start and settle in your aquarium. This is something that happens naturally in the wild. The nitrogen cycle refers to the course that ammonia, nitrite, and nitrate take. Here’s a simple breakdown:

-Waste breaks down into ammonia

-Bacteria breaks ammonia down into nitrite

-Bacteria breaks nitrite into nitrate

Ammonia > Nitrite > Nitrate

It’s important to have an established cycled tank before adding your fish so you have a safe environment, where the toxic ammonia and nitrite are processed by your bacteria colonies.

You can figure out these levels with liquid test kits.

You can also use test strips, but they’re usually incorrect.

Visible biofilm ⬇️

The bacteria that I mentioned is called “beneficial bacteria”. It essentially runs your tank. This bacteria creates a coat on things in your tank called a “biofilm” that is usually not visible, but is sometimes very apparent. The best place for the bacteria to grow is the stuff in your filter, called filter media.

To avoid destroying the bacteria in your filters, only clean your filters when they’re clogged. Clean them by using tank water emptied into a bucket instead of tap water that’s chlorinated (chlorine kills bacteria).

Coming soon

More on filter media

Now that you understand what the nitrogen cycle IS, let’s learn how to cycle.

Start with adding a source of ammonia to your fishless tank.

Most people just add fish food to break down into ammonia; alternatively you can use bottled ammonia. You also need a source of beneficial bacteria; you could do it without this, but it takes much longer to colonize. An amazing way to add bacteria is an old filter pad. You could get this from a local pet store, or maybe a friend. Just please be careful doing this, make sure the source doesn’t have an illness or other harmful aspects.

Next best is bottled bacteria; I always recommend this one. Now you play the waiting game.

Test your levels every day or so, you’re waiting for ammonia to start showing up. Once this has happened, in the next few days you’ll start seeing nitrites, then finally nitrates. Once nitrates are present, just wait for your levels to be:

Ammonia 0

Nitrite 0

Nitrate under 20

To bring these levels down, you can do water changes by taking a siphon and draining water. To avoid disturbing the bacteria you just built up, do not scrub or touch surfaces.

Then you can start adding fish! Introduce fish slowly to make sure your new bacteria colonies can handle the “bio load” of your fish’s waste deposit.

Steps:

-Add a source of ammonia and beneficial bacteria

-Monitor your levels

-Ammonia shows

-Nitrite shows

-Nitrate shows

-Wait for levels to be safe

-Add fish!

What we just went over is called a fishless cycle. You could also do a fish-in cycle, but this is considered cruel because of the toxicity.

Coming soon