How to cycle a fish tank

RULE: Before we can keep fish, we need to know how to cycle a fish tank. Without this process, fish around the world will be dying in schools.

How To Cycle a Fish Tank is here to help – I will walk you through the whole process the best I can to get your new tank up and running in no time at all (well, some time, actually).

If you are anything like me, you would be one of those enthusiasts that wake up one morning, decide “I want a new fish tank.” Run out to the store, get a tank, and pick up some fish too. MISTAKE!

A Deadly Unseen Assassin in your tank

The moment you introduce new fish to a tank, they will start producing waste in the form of Ammonia. This is harmful to your fish – the Deadly Unseen Assassin of fish all over the world.

The only thing that can convert unhealthy ammonia into a non-toxic element is bacteria. And that is why we have to cycle a new fish tank; to start, grow and maintain a healthy bacteria colony in your tank to take care of the nasty stuff.

There are essentially two ways to cycle, and I am lucky enough that someone taught me both methods many years ago. Today, I still use both methods successfully, depending on the time I want to cycle a new tank.

No matter which of the methods below you decide on, the fact remains: You Have to Cycle a New Fish Tank – Always!

Fish Tank
A Cycled Tank

The Two Cycling Methods in a Nutshell

  1. Cycling with Fish: This method was the first one I learned and is the most natural cycling method. It does take a bit longer than the second method, but at least you have some fish to keep you company while you work through the tedious task of cycling – which can take anything between six and eight weeks.

There, the bad news is out there, and I cannot take it back. Now you know how I felt the first time I heard it takes so long before I can stock my tank with schools of pretty fish.

  1. Seeding a Tank: In this method, no fish are involved, and anything from chemicals to “borrowing” some healthy bacteria from an existing tank is used. I will not be discussing introducing bacteria through the substrate, plants, or other methods, as I always only borrow bacteria colonies from filter media.

This method can get you through the cycling process a bit quicker. It is a bit riskier, though, and a mistake could break the whole process, making you have to start from scratch.

I always tell people it’s almost like an organ transplant – you must have your timing JUST RIGHT to be successful. We will be transferring a live colony from one tank to another after all.

Cycling a tank with Fish

I know, I know – many people will want to throw me with a shoe or a large fish tank of some sort. Cycling a fishless tank is the preferred way of going about it. But hear me out. Cycling with fish is not as terrible and inhumane as many people say it is.

I have set up hundreds of tanks for customers and myself, and the losses of fish were no greater than the natural loss of fish during a tank’s life span.

We use only the toughest little soldiers out there, and they have proven themselves to withstand the cycle process and the stresses accompanied by it. Trust me – they get through and live long, happy lives once we are done with the process of cycling.

Let’s go:

At this stage, you should have the following done already:

  • A new tank is assembled and placed where it will “live” in your house.
  • It is filled with conditioned water
  • The filter is up and running
  • The substrate and plants are all in their places
  • The heater is installed and operating

Now, run out to your local pet shop and get one or two of the following fish (and these are only the ones I use or recommend, some fish can also work, but let’s stick to what I know and am comfortable recommending to you)

  • Zebra Danio (my first choice), not the prettiest, but REAL tough ninjas.
Zebra Danio
  • Tiger Barb – See, now they are pretty and rather fun to keep you company through the cycling weeks.
Tiger Barb
Tiger Barb
  • And the prettiest for last: Banded Gourami (also called Dwarf Gourami in some countries). Even while cycling, you can have a beautiful fish in your tank – see, not so bad after all.
Banded Gourami
Banded Gourami (Trichogaster fasciata)

Remember, you don’t want to put too many fish in the tank, as they will create too much waste for a starting bacteria colony to process. I add two or so to the new tank.

IMPORTANT: Please do NOT overfeed your fish during the cycling process, as leftovers will cause excess rubbish in your tank, placing a heck of a load of extra workload on your already “struggling just to get their job done” bacteria.

While at the shop, please get yourself a proper testing kit, too, because you will be testing your tank’s water to DEATH over the next couple of weeks.

And Then The Testing Starts

Start testing the day after you put in your first fish.

Here is what will happen immediately: The toxins are known as Ammonia (that Unseen Assassin). Nitrites will sky-rocket the first couple of days as your fish start using the toilet regularly (bless them). But all is well in the bacteria colony, as it starts feeding off the toxins, starts growing instantly (OK, bless them too).

Over the next couple of weeks, test, test, and test some more. You will notice that while the pesky Ammonia and Nitrites start to decline, there should be an equal incline of Nitrate, which is better for your fish.

It is imperative to do regular water changes during this phase. 10% to 15% at the most, as we don’t want to upset the fish too much. Also, be sure to condition and dechlorinate the water you add and have it more or less at the same temperature as your tank water. Changing the water regularly plays a significant role in the bacteria colony’s growth.

Once both Ammonia and Nitrites are hardly noticeable in the tests, your cycling is about to come to an end – YAY.

Tip: I use the API FRESHWATER MASTER TEST KIT all the time.  Accurate, simple to use, and most importantly – available at Amazon.

Adding More Fish
Fish Tank
Fish…And More Fish

Now that both Ammonia and Nitrite levels are as close to Nothing as possible, and it stays there for a day or three, your tank is ready to welcome more occupants.

Now remember, AGAIN, you cannot go out and get hundreds of fish for your tank just yet (or ever, just joking). You will still have to introduce small numbers of fish at a time. I wouldn’t add more than three fish every week or so until the tank is at capacity. This is to prevent overworking that healthy and happy bacteria colony we worked so hard on establishing.

From now on, it is basic maintenance of your tank, regular testing, and regular water changes.

Seeding A Tank

So this one is interesting and a bit quicker than the process above – BUT – you have to have your timing perfect. Remember what I said before? It’s a lot like an organ transplant in humans.

Ugly as they look, smelly as they are – trust me when I say bacteria are the superheroes for your fish, thank you. Keep them healthy and happy, and your fish and tank will reward you with infinite pleasure.

Seed You Ask

Everything works the same as before, but we kick start our bacteria colony.

It boils down to finding HEALTHY bacteria from an existing tank and filter media preferably. There are other ways to get bacteria to your tank, but as I said, I only cover what I know works and what I use with each new tank for customers or myself.

Just a note or two on the acquisition of the bacteria. Just like we won’t want a smoker’s lungs or a heavy user of alcohol’s liver, we don’t want sick or struggling bacteria in our new tank.

Here is what I do, and if you can do it, go for it, try it. I am a regular at a couple of local pet shops, and of course (for obvious reasons to follow) very familiar with all the staff, even friendly with most. I stalk the shop silly and have regular stakeouts to make sure I target a healthy tank.

When it is time to get my grubby little paws on some healthy bacteria, I conjure up all my charm and finesse and ask my friends at the store if I may please get a small piece of filter media with some healthy bacteria. Without bragging: I’ve never been denied access to some fine bacteria. Of course, I replace their media with new media immediately for them.

Now, the bacteria must be kept ALIVE during the transit home, so there is no time for tea and cookies. Grab that filter media, pop it in a bag (same as when you buy fish) – and rush home! If I had sirens and red lights on the roof of my car, they would be going crazy.

Isn’t she Beautiful?

Back home, you pop the new media, preferably the same as what you are using in your tank, in your filter, and VOILA, the start of a colony.

It is vital to add your cycling fish as soon as possible to keep the colony alive, so maybe grab a Danio or two on the way out of the shop.

The whole testing phase as mentioned above still applies, but you will notice that things happen much quicker. Just don’t kill your new colony of bacteria by overfeeding the fish or doing too large water changes.

Nurture those critters the best you can, and they will keep your tank sparkling clean and your fish happy and healthy for a very long time.

I would love to hear from you on this subject, so please leave a comment below, and let’s chat about this…