The Nitrogen Cycle

The Nitrogen cycle is a natural pathway to organic decomposition. This pathway has to be completed both quality wise and quantity wise, in order to provide the bacteria foundation necessary in assuring success within our aquatic systems.
As Hobbyists it is important to incorporate this concept when maintaining the aquatic environment.
There are many different types of bacteria that naturally occur in any environment, all in competition to establish a foothold. Our focus here will be on the beneficial bacteria types and their establishment in your system.

What Is The Nitrogen Cycle?

Like all living creatures, fish give off waste products (pee,poo, and gill ammonia excretion). These Nitrogenous waste products break down in ammonia (NH3), which is highly toxic to most fish. In nature, the volume of water per fish is extremely high, and waste products become diluted to low concentrations. In aquariums however, it can take as little as a few hours for ammonia concentrations to reach toxic levels, this is when your problems as a new fishkeeper to the hobby start to occur, and as a result, fish loss may start to occur, and you end up here looking for help, don't feel like you've done anything wrong, most times its lack of education prior to starting this hobby, which is not offered by the local fish stores to the general public, either by lack of education themselves on the hobby, simply not caring, or they are on commission based sales and are out to get as much money from your sale as possible, this is "VERY" common, you are not alone, and this is why we are here to help with honest answers to your questions as we can provide, based on personal experiences in this hobby. The first thing you need to get is a Master Test Kit, this will reduce your drama as a beginner ten fold by knowing what you're looking for and educating yourself in the process through these tests as the changes occur.

How much ammonia is too much?

The quick answer is:
If a test kit is able to measure it, you have too much. There is a possibility at this point of stressing the fish.
 A more detailed view of ammonia toxicity can be found later in this explanation of the cycle.
The Nitrogen Cycle itself is the biological process that converts ammonia into other, relatively harmless nitrogen compounds. Fortunately, several species of bacteria do this conversion for us. Some bacteria convert ammonia to “nitrite”, and then to “nitrate”. Thus cycling the tank refers to the process of establishing bacterial colonies in the filter bed that convert the ammonia to nitrite, then nitrate.
The desired species of nitrifying bacteria are present everywhere. Therefore, once you have an ammonia source within your tank, it’s only a matter of time before the desired bacteria establish a colony within your filter bed.

The most common way to do this, and this is a disputed issue indeed, is to place one or two hardy and inexpensive fish into your tank after all is set up. The fish waste contains the needed ammonia on which the bacteria feed on to colonize and reproduce.
This is disputed I say by fish keepers who use the “fishless cycle” as a rule, but we will not get into that information on this page, we have provided another page/link with information on the fishless cycle if this is the way you should choose to go. Chances are you as a beginner, have already purchased fish and this is why you are here. If you desire more information on the “Fishless cycle”, we will be happy to provide you with the tools necessary to do this route as well.
 

Do Not Overfeed your new fish!!!!!! This is a common mistake with new fish keepers, the more food the more ammonia being produced, and will raise the toxic levels too high and too rapid for your fish to withstand. This may lead to undesired fish loss, sadness, and discouragement within your new hobby.
Also steer clear of feeder fish to use for this process for their overall health may bring unwanted disease into your tank as well as unwanted fish loss.
Some recommended breeds of fish for cycling a tank are White Cloud Minnows, Zebra Danios, and almost any species from the Mollie, Wag, and Platy family.
Keep in mind also that for Coldwater tanks, Goldfish, White Cloud Minnows, and Danios, can be used. Not the others mentioned however, for they are Tropical fish and require a temperature of no less than 76 degrees and a salt level as well for their health and well being. Also keep in mind that most of these fish are live bearing fish, by this I mean they give off live offspring, and as a result your new tank can be easily overpopulated in a short time due to breeding habits of these fish and broods occurring every 21-28 days

During the cycling process, ammonia levels will go up and then suddenly plummet as the nitrite-forming bacteria take hold.
Because nitrate-forming bacteria don't even begin to appear until nitrite is present in significant quantities, nitrite levels skyrocket (as the built-up ammonia is converted), continuing to rise as the continually-produced ammonia is converted to nitrite.
Once the nitrite-forming bacteria take hold, nitrite levels fall, nitrate levels rise, and the tank is fully cycled.

Your tank is fully cycled once nitrates are being produced (and ammonia and nitrite levels are at zero).
To determine when the cycle has completed, you'll need to test with Nitrate test kit (see test kits section) and measure the levels yourself, or bring water samples to your LFS.
The cycling process normally takes anywhere from 2-6 weeks. At temperatures below 70F, it takes even longer to cycle a tank.
In comparison to other types of bacteria, nitrifying bacteria grow slowly.
Under optimal conditions, it takes a full 15 hours for a colony to double in size.

The exact concentration at which ammonia becomes toxic to fish varies among species; some are more tolerant than others.
In addition, other factors like water temperature and chemistry play a significant role.
For Example, Ammonia continually changes to ammonium and vice versa, with the relative concentrations of each depending on the water's temperature and pH.
Ammonia is extremely toxic: ammonium is relatively harmless. At higher temperatures and pH, more of the nitrogen is in the toxic ammonia form than at lower pH.

Standard test kits measure total ammonia without distinguishing between the two forms.
The following chart gives the maximum long-term level of ammonia-N in mg/L (ppm) that can be considered safe at a given temperature and pH.
Again, note that a tank with an established biological filter will have no detectable ammonia;
this chart is provided only for emergency purposes. If your levels approach or exceed the levels shown, take emergency action IMMEDIATELY!

Speeding Up Cycling Time
(For the impatient)

The nitrogen cycle can be jump started in a number of ways. However, this requires the access of another well-established tank in order to do so.
The basic idea here is to find an established tank, and take some of the bacteria out of it and placing in the new tank. Most filters have some sort of foam block or insert in which nitrifying bacteria attach and colonize in. borrowing all or parts of such an insert and placing it in the new tanks filter, gets things rolling more quickly.
If the established filter tank uses a Undergravel filter system, nitrifying bacteria will be attached to the gravel as well, and in this case you can;
Take some of the gravel (a cup or more) and hang it in a mesh bag or woman's knee-hi directly in your filter if you can. If not lay it on the top of the gravel in your new tank if this tank as well has a Undergravel filter system.

If you have a new box, canister, or corner filter system. You can hang this new filter on the already established tank for a week or so and this will cure the filter and establish bacteria within it for you to then put on your new tank.
More recently, products containing colonies of nitrifying bacteria have become available at most LFS’s (Local Fish Stores) In theory, adding the bacteria, jump-starts the colonization process we have shown above. Net feedback on this is mixed as some people report success and swear by it, while others report they do not work at all. In principle, such products should work well, however nitrifying bacteria can not live without oxygen and food. Thus, the effectiveness of such products will depend on its freshness and can be adversely effected by poor handling such as too hot or too cold variables. Unfortunately, these products do not come with a freshness date stamped on them, so there is no real way of knowing whether your purchase of them will be one of those affected. For someone setting up their first tank however, all fish will probably be purchased from the same store, so the danger then would be relatively small as the all the newly purchased fish will have already been exposed to these pathogens.

We hope this has been worded in terms you can easily understand, if you should have any questions regarding any terms used here, please feel free to email us direct or place a question regarding it in the Loaches Lounge on our message board.
Thank you for taking the time to educate yourself on this wonderful hobby!!!! We hope you’ll enjoy it as much as we do, and we look forward to chatting with you about it!!!