Cycling Put away your Schwinn or your Trek. You won’t need them for this article. We’re talking about water cycling, and this one’s important, so get a good cup of coffee and let’s get cracking.
If you’ve been reading this series on home aquaculture, you’ll remember that last week we talked about the fact that fish can’t escape their watery homes. They breathe the same water that they poop and pee in. Nasty right? Well, we need to talk about that. Because this is the essence of fish keeping. This right here is what will make you succeed and have hundreds of pounds of fish that you can harvest from your backyard, or fail and have a disgusting mess that your spouse will threaten to leave you over unless you get rid of it.
Cycling. What the devil am I talking about?
Cycling is a natural process. It is the process or "cycle" that takes fish waste, pee and poop, and turns it into harmless Nitrogen gas that escapes into the atmosphere. It is the process that keeps your water clean. Your filters help, yes, but if you have not cycled your fish pond or tank, no filter on Earth will keep your fish alive.
So, if it’s not a filter, what do I have to add?
Ok... Do I buy any new equipment?
What do I have to do?
Ok... so I don’t do anything, I don’t buy anything, I don’t add anything. Why am I reading this? Let’s move on. Next article.
Not so fast pal. THAT right there is why most people fail in cycling a fish system. Confused? Most people are. But you shouldn’t be.
Cycling is a biological process, where bacteria grow on the surfaces of your tank and the objects in it. These bacteria are there because there is food in the water. You guessed it. They eat fish waste. There are several different types of these bacteria, but the simplest way to explain it is they each eat different things. Each step in the cycle is this: the development of a new colony of bacteria that will eat the products of the previous step in the waste cycle. That means, one bacteria will eat the fish waste and produce a waste product itself. Another bacterium will eat THAT waste product and in turn produce another one. And so on, until the product is Nitrogen gas. That’s it. That’s cycling.
Where do these bacteria come from? Do I add them?
Nope. They are already there. They are in the air. On the surfaces of the tank. On your hands. They’re everywhere. You don’t have to add a thing.
OK. Enough confusion. I’m going to show you the exact steps that happen, and then once I’ve shown them, we’re going to talk about each of them and what you have to do.
But you said I have to do nothing.
Ok, I lied. But barely. Because most of what you have to do is be patient. And for most people, that’s really hard.
These are the exact steps of cycling:
N →NH4→NH2OH →NO2 →NO3→NO2→ NO → N2O → N2
Ok, now I know that looks just awful and you’re probably expecting a lot of hard chemistry explaining each step in the equation, but I promised I would keep this as simple as I can and I will try to keep that promise.
If you look at the steps you will undoubtedly say: "Wait a minute, I start with Nitrogen (N) and end up with Nitrogen gas (N2). This equation starts and ends with the same thing!" If you did say that, I congratulate you, because that is what the equation shows. But the N on the left represents fish poop. It symbolizes Nitrogen in waste form. Either as urea from pee, nitrogen in waste, uneaten food etc.
Yes. Nitrogen. Without getting too deep into chemistry, let me just say that Nitrogen compounds if you are a chemist are called "Amines." And that should sound familiar because it’s the same "amines" in Amino Acid. For the bodybuilders out there, you just figured it out. For the rest of us, we have to take a glimpse back into high school chemistry. Amino Acids are the building blocks of protein. Protein are the building blocks of Muscles. That’s why Nitrogen. Because Nitrogen compounds are one of the basic compounds you get from food. The other two are Carbon compounds (sugars) and fats which are chemically very structurally similar to Amines in many ways, but which contain no Nitrogen. All three of these compounds chemically are all extremely similar to each other and they form part of the field of biochemistry. But I promised this was going to be simple. For the curious among you, feel free to follow the links. And for the super curious, let me just say that the reason that you don’t have aquarium cycles for sugars and fats is because they are removed differently. Sugars are burned off biologically into Carbon Dioxide (a gas which directly escapes from the water) and fats are primarily removed by filtration.
Ok. So we’ve established that we are talking about Nitrogen. This Nitrogen is in the form of wastes. So the first step in our equation is turning that nitrogen into NH4. This is important. This is the first step, and it’s a doozy. NH4 is Ammonia. And its toxic as hell.
The fish poop is gross. The ammonia is lethal. How lethal? 0.045mg per liter will kill your fish. Let’s put it this way: If you can detect it, your fish are dying. If I opened a jar of ammonia in your house,
you’d know it almost instantly. As a matter of fact, Ammonia is what you smell in smelling salts which will wake you up if you are unconscious. Think about that for a second. Your body is brought back from unconsciousness by just the smell of Ammonia. So, yes. It’s very toxic. And it is one of the byproducts of protein metabolism. It’s the reason why your cat’s litter box smells like it can wake the dead. Because cats pee Ammonia. And fish? They don’t pee it. They release it from their gills. So, the start of our equation here is either from fish poop or uneaten food which a bacteria digests and turns into Ammonia, or Ammonia from the fish directly. Either way its Ammonia. And it will build up in the water. And build up. Until there is enough of it that a second bacteria starts to grow. This one takes the Ammonia, and through a series of biochemistry turns that Ammonia into Nitrite. In our equation, that’s NO2. So right now, we are here:
N →NH4→NH2OH →NO2
And the reason why we are stopping the equation here is because Nitrite is the next important chemical. The NH2OH is an intermediate step that happens inside the bacteria. We can ignore it. Let’s just say, when the bacterium eats Ammonia, it converts it in its body to NH2OH, and when it is finished it releases NO2 as waste. If you thought Ammonia was bad, wait till I tell you what this does. Nitrite. What a lovely chemical. It binds to hemoglobin. Hemoglobin is the compound that makes your blood red. It’s the compound that carries Oxygen. Giving Oxygen to the hemoglobin in your blood is THE reason why you and I have lungs. Nitrite attacks it, binds with it, and makes it so hemoglobin cannot carry oxygen. Nitrite will make your fish die of oxygen starvation, of asphyxiation, even though there is oxygen all throughout the water. And the worst part of it is, the concentration of nitrite in the water needed to cause death is very low. 121mg per liter. Shall we move on?
N →NH4→NH2OH →NO2 →NO3
Our next stop: Nitrate! Do not confuse Nitrite with Nitrate. Nitrate is far less toxic. 1565mg per liter. There will always be Nitrate in your water. Don’t sweat it unless the concentration is high. If it is, it is telling you that something is wrong. Either your system crashed, or you suddenly started feeding way too much, or your fish system has not finished cycling. If you detect Nitrates in high concentration, there’s a problem. But don’t get upset if you see some. It will always be present.
Ok. So now what?
Well, here’s where I tell you a fun fact. The equations we just reviewed happen inside bacteria, but they happen in bacteria that are in the presence of oxygen. These bacteria breathe. These next equations also happen in bacteria. But they happen WITHOUT oxygen. That is, these bacteria do not breathe. They are anaerobic. This has implications that I will discuss at the end of this article, when I tie all these threads together for you. For now, just keep in mind, all of the next step happens without oxygen.
And here is the step:
NO3→NO2→ NO → N2O → N2
Wham! All at once. All of these steps happen inside a bacterium all in one go. If you notice, you’ll see that our Nitrate (NO3) is turned back into Nitrite! (NO2) What? Why? Don’t worry about it. It’s an intermediate step. It happens inside the body of the bacteria as it "digests" the Nitrate. The important part of this step is that the bacteria releases N2. Nitrogen gas, which escapes into the air. We’re done. If
you want to read more about it, and I do suggest it for those of you who are curious, you can read about it here: http://www.advancedaquarist.com/2011/4/chemistry
So, the fundamental steps are: