The Aquarium Nitrogen Cycle

For my first real post, I'm going to talk a little bit about cycling aquariums. Not only the cycle of a new tank itself, but the basics of getting a tank set up and ready to house fish in it's water.

It's happened to many people, they go to a pet store fully expecting to leave with they're tank, equipment, decor, and an entire stock of random fish that day. They get there, however, to find that it's not that simple! The store assistant tells them "you have to let the tank 'cycle' first." What that means, the customer is completely clueless, and usually they get little or no further explanation. "Cycling" is a term that I've seen thrown around quite loosely, what it should refer to is the nitrogen cycle, but what it sometimes refers to is simply the settling of the water in your tank over the course of a few days.

And there are reasons for that. 1- No one wants to wait two weeks to get fish. They want their tank to be beautiful and stocked NOW. (don't we all?) and 2- You need fish or some other form of waste in a tank to REALLY start the cycle.

Allow me to explain.

When most people first set up a tank, they used water straight from the tap treated with water conditioner. If not that, other people use rain water or Reverse Osmosis (R.O.) water, both of which come with their own inherent issues and advantages. For now, let's assume it's tap water. When water come out of your faucet, it is a certain pH and hardness. If you let it sit or "settle" over time, that original pH and hardness will change. Proof? Leave a glass of water out overnight, then take a sip the next day. It tastes different, most people think it's stale, but it's really just altered a bit chemically.

That is the reason you let your tank sit with a filter running for a few days. You don't want to put fish into a new tank that is going to change pH drastically in a matter of hours. It's way too stressful for them and usually results in death or illness. Remember that there are many fish illnesses already in your tap water, and becoming stressed out is the thing that makes fish susceptible to them.

Now, you've had your tank sitiing and filter running a few days. What's next? Fish?! Maybe, it depends on how you want to tackle the cycling issue. Cycling is all about the beneficial bacteria you want to establish, and in order for them to develop in your tank you're going to need to introduce waste. Some people cycle their tank with no fish, instead they put fish food into the tank and let it rot away, creating waste. Waste creates ammonia, which is the first step in an aquarium's cycle. Others use straight ammonia from a bottle and carefully monitor how much goes into the tank over a period of time, another way of cycling with no fish introduced.

I've never attempted any form of fishless cycling, so I'm probably the wrong person to ask about it. I have always picked a hardy species of fish (preferably one I plan on keeping once the tank is cycled) and added just a few of them. You can also supplement with a product called "Tetra Safestart," it introduces the beneficial bacteria to the tank from the start, and makes the cycling process faster and safer for the fish.

What I've found is this; fish are okay in a cycling tank as long as the following conditions are present...

1- No more fish are added during the cycling process
2- The changes happening in the water are slow, this will happen if no other fish are added in the process
3- The fish you cycle with are hardy and healthy

Alright, we've covered how you cycle, but what should you look for while your tank cycles? I can answer that too...

When waste is introduced into your tank in any form, it breaks down and creates ammonia. Ammonia is unsafe for fish, and can cause sickness and death in many cases. It is undesirable in any amount in any aquarium, obviously, but as I stated above, as long as the cycle is done slowly and steadily, any fish present in the cycle will be able to take the ammonia. That change in the water will be slow and consistent, and if you use a product like Safestart, the levels of ammonia you see will be lower.

So you will see the ammonia levels in your tank rise, as you should be testing the water periodically during the cycle. Once that happens, bacteria called nitrosomas will form in your tank and oxidize (eat) the ammonia, the waste created from this oxidizing will form nitrites. You'll see the ammonia in your water tests going down, and nitrites going up.

Soon after that, a new bacteria will develop and convert the nitrites in your tank into nitrates. The names of the two are very similar, but the effects they have on fish are very different. Think of nitrites as the evil twin of nitrates, at any level they will harm fish, but nitrates are safe at lower levels which are easily maintainable. You'll always have nitrates in your tank to some degree, and once your nitrates are gone and nitrates have appeared in your water tests, your tank is cycled!

"Now Luci," you say "this is an awful lot to remember... And how long does it take?? It seems aquariums are just a big waiting game!" Well, yes, they are. At least your not waiting for bonsai trees to grow though, that takes forever! Fish do take time, and if you take the time to allow your tank to cycle and your fish to settle, you will have many less problems than if you are not patient. Trust me! I've learned all of this the hard way! It's much more trouble and MUCH more money if you don't wait.

That being said, cycling typically takes about 2 weeks to a month. Depends on the fish you use to cycle, the size of the tank, and pretty much everything else. I cycled my 70 gallon with 5 female bettas, and it took about a month or so. Not to bad, eh? (You're probably saying "YES! A MONTH IS A LONG TIME!!" hehe)

The simple version is this, let your tank sit a few days, add a minimal amount of hardy fish (preferably a species you would like to keep after you cycle), wait for nitrites to go away in your water tests and for nitrates to show up, BAM! cycled.

And what do you do after that? Start stocking of course! Add a few fish at a time so you don't upset the balance you've worked so hard for, and start doing water changes if you haven't already. How many water changes and the amount of water you change is all about how many fish you have. The less you have the easier it is, also the bigger your tank the easier it is. I change my 70 gallon every other day about 20-40%, that's because I have discus and they're very sensitive fish. Most people can get away with water changes every few weeks to a month.

That's all for now guys, hope this helps anyone who might have been confused, or if not it might have confused you even more! If I left anything out or you think I got something wrong, feel free to let me know!