Aquarium Nitrogen Cycle, Start Cycling Aquarium Guide

Cycling your aquarium is the first thing, and the most important thing you must do to provide a healthy and stable home for your fish!

Aquarium maintenance is easy if you have an aquarium nitrogen cycle going on. The aquarium cycle is more commonly known as the nitrification process and is the biological filter for your tank. Aquarium filtration systems work to keep your water pristine and provide a safe home for your fish, and the biological filter is perhaps the most important filtration system to have. 

There are three methods of cycling an aquarium covered in this article.

In the table below there are Three Methods for Cycling a New Tank, but first let's look at why you want to have a biological filter and cycled your tank. Let's explore what the aquarium nitrogen cycle is and how it works. Then we'll cover some important things to watch out for to keep it working!

• Why cycle your aquarium

The nitrification cycle is actually pretty simple. It can seem hard because of a couple terms that are not familiar in our everyday language. But basically this is a simple three-step process. 

1.      Step One The first thing that happens when you put fish in the tank is ammonia is produced. This is from the fish waste or excess foods that are decomposing.

2.    Step Two As the amount of ammonia starts to increase, a bacteria forms called nitrosomonas. This bacteria begins to convert the ammonia into nitrite. As the ammonia is converted to nitrite, the amount of ammonia will begin to drop and now the nitrites will begin to rise. Soon your ammonia test will show no more ammonia in your tank. This usually happens within the first week and a half of a normal cycle. Nitrite is also very toxic to fish, though not as hazardous as ammonia.

3.    Step Three As the nitrite levels increase, another bacteria forms, called nitrobacter. This second bacteria begins to convert the nitrite into nitrate. As it is converted to nitrate, the amount of nitrite will drop and the nitrates will begin to rise. Soon your nitrite test will show no more nitrite in your tank. This happens between three to six weeks in a normal cycle. Nitrate is harmless to fish but is one of the nutrients that plants and algae need and is the final product produced in the nitrification cycle. One of the reasons that water changes are recommended is to keep nitrates at lower levels.

The time it takes to cycle an aquarium can be sped up by 'seeding' the aquarium with commercially prepared bacteria. Then the entire cycle will only take between 1 - 2 weeks. This seed bacteria is available in either a freeze dried or liquid form. You can also add bacteria rich media from an established aquarium, like some of the gravel. The seeding should be done after ammonia is starting to form in the newly setup aquarium. You must wait until there is ammonia or the seeded bacteria will starve.

• Simple! How the nitrogen cycle works

Nitrate is the end product of the nitrogen cycle. The simplest way to remove nitrates is through regular water changes. For the most part nitrate is not harmful to fish unless in enormous quantities and for prolonged periods of time, and even then it is only some types of fish are at risk. You will most likely not run into this problem in a regular home aquarium.

   Nitrates can actually be beneficial if you have live plants, as it is a nutrient for them. Tanks without live plants to utilize this nutrient however, can get excess algae growth. This holds true for both freshwater and saltwater fish only aquariums, but not for the reef aquarium. Nitrates are usually strictly controlled in the reef aquarium because they can cause undesireable algae growth.

• What about the nitrates produced

Nitrate is the end product of the nitrogen cycle. The simplest way to remove nitrates is through regular water changes. For the most part nitrate is not harmful to fish unless in enormous quantities and for prolonged periods of time, and even then it is only some types of fish are at risk. You will most likely not run into this problem in a regular home aquarium.

  

Nitrates can actually be beneficial if you have live plants, as it is a nutrient for them. Tanks without live plants to utilize this nutrient however, can get excess algae growth. This holds true for both freshwater and saltwater fish only aquariums, but not for the reef aquarium. Nitrates are usually strictly controlled in the reef aquarium because they can cause undesireable algae growth.

  

• What is needed for success

Besides fish that are producing ammonia, there are two important things the nitrogen cycle depends on: 

1.      Needs a place for beneficial bacteria to live and grow: When you set up your aquarium you will be using a filter of some sort which will provide a home for this bacteria. The most common filters are undergravel filters, external filters, or internal filters. Each of these has a media with a lot of surface area for the bacteria to live and grow on. On the undergravel filter the media is the gravel itself, other filters use some sort of synthetic filter media, such as foam or filter pads.
   The most important thing to think about when choosing the media is that it provides a lot of 'surface' area for the bacteria colony to grow on. Sponges are laced with holes so a lot of surface area is created inside the entire sponge, pads are similar.

2.    Needs oxygen to survive:    The higher the oxygen content of the water, the healthier the bacteria will be. To have oxygen in your water, the water needs to be flowing. Where the water is exposed to the air, usually on the surface, an exchange happens. Here other molecules in the water rise to the surface and are exchanged with the oxygen molecules. Then your filters pump moves the water through the aquarium, and the newly oxygenated water flows over the bacteria.

• Tips to keep your tank cycling

Once your tank is cycled there are some things to be aware of so that you don't loose your beneficial bacteria. When the bacteria is removed or dies, the ammonia levels begin to rise and you can quickly lose your fish.

• Make sure your pump (filter) is always working. Water that is not moving becomes stagnant. If your pump quits or the water stops flowing for some other reason, it is estimated that it takes about 6 hours for the bacteria to die from lack of oxygen.
• If your filter media becomes exposed to air and dries out your bacteria will die.
• When you remove the sponge or pad media from your filter to clean it, you can easily wash the beneficial bacteria off of it. It is best if you have two sponges or pads. This way you can swap between the two each time you do maintenance, cleaning one and leaving the other. Next time you do maintenance clean the opposite one. It takes about 1 - 2 weeks for a cleaned pad to re-colonize when there is a healthy colony still in the aquarium.
• When you remove the sponge or pad media from your filter to replace it, you loose all the bacteria growing on it. Again it is best to have another sponge or pad, and only replace one at a time.

Aquarium Nitrogen Cycle

 

Described here are three different methods to cycle your aquarium.

You will need to monitor the ammonia and nitrite levels (using test kits) throughout the cycle period, until they are both zero (or very close to zero). When they are both zero, the aquarium is cycled and is safe for fish.

Method 1  : Cycling with fish

This first method is the classic 'traditional' method used for many years. It cycles the aquarium using inexpensive hardy fish. Hardy fish to cycle an aquarium with include Danios, Platies, and even goldfish.

1. Traditional Method:

1.      Have the temperature stabilized at 74° to 80° F(26° - 28° C).

2.  Place 1 hardy, inexpensive fish for each 2-3 gallons of aquarium water. Inexpensive fish include danios, platys, barbs, mollies, etc. These fish will provide the initial ammonia to get the biological filter started (see Biological filtration above). This should take about thirty days to six weeks.

3.   This can be stressful to the fish, especially if you add large numbers of fish. Fewer fish will be less stress as changing water parameters go slower and they have a chance to adjust.

4.  After about six weeks, when the aquarium has "cycled", you can add additional fish (see nitrification cycle under Biological filtration above).

Method 2 and 3 : Fishless cycling (Cycling an aquarium without fish)

 These next two methods cycle the aquarium without the use of fish. One is with the use of ammonia, and the other is with the use of fish food.
These points apply to both of the non-fish methods:

• Higher temperatures of 86° - 95° F ( 30° - 35° C) can be used for optimum bacteria when cycling without fish, but you must stabilize the aquarium slowly back to lower temperatures before you add fish.
• You can speed and enhance the nitrification process by introducing a starter culture of bacteria. One way to do this is by is seeding the aquarium with some gravel or filter media with existing bacteria from an established aquarium. Another way is by adding commercial preparations of nitrifying bacteria, there are several different brands available at pet stores.

2. Cycling using ammonia:

1.    Introduce pure ammonia to cycle the aquarium. You can buy unscented ammonia with no additives from a supermarket or a bottle of ammonium chloride.

2.  Add ammonia from a dropper, 3 - 5 drops per 10 gallons of water per day to get and maintain a reading of 5 ppm.

3.    Initially there will be no nitrites. Monitor nitrites daily and continue the daily ammonia dose until you get a nitrite reading. At this point you can reduce the daily amount of ammonia to 2 - 3 drops per 10 gallons. Continue this until both the ammonia test and the nitrite test reads 0 ppm.

4. This method can take as little as three weeks or up to six weeks to complete the nitrification cycle, but adding a starter culture as described above can speed the time up considerably.

5.    When the cycle is complete reduce the temperature slowly back to 74° to 80° F(26° - 28° C). Reducing it quickly can stress the bacteria.

6. Do a major water change, about 90%, and add activated carbon to remove any possible additives which might have been in the ammonia.

3. Cycle using fish food:

We are not as familiar with this process and there is less information available on specific details. Basically it works as follows:

1.  You simply feed the tank with a fish food, presumable daily to keep an   ongoing decomposing process. As the food decays it will to produce ammonia and get the biological filter started.

2.   This method takes about the same amount of time as the fish method above.

3.   The main drawback to this method is that it is difficult to get a large enough initial bacteria colony. So when you introduce the fish, they may add a larger ammonia load than the colony can handle. Consequently you may get some additional ammonia and then nitrite spikes, though they should be less dramatic and shorter lived than the initial cycling spikes.

4. Another drawback is that the decaying food, besides producing ammonia, can add other by-products such as phosphates.

Basics Of fresh Water Aquariums

1. Choosing the Right Aquarium: 

    Although it is important to choose an aquarium that you think will look good in your living room, there are other equally important considerations that affect the ongoing expense as well as the health of the inhabitants!

In general we have found that stability of the environment is the most important secret to successful fish keeping. A lot of material has been written about the ideal environment for various species of fish, whether they like warm water or cold water, high Ph or low Ph, hard water or soft water, but this is generally useful only if you are attempting to breed the fish or are planning on keeping a very sensitive fish that is known to be challenging. In choosing all of the items and the fish themselves, always keep in mind the stability of the environment.

 2. Size of the Aquarium

    Always choose the largest size that fits your living room and your budget! 

Don't be fooled into thinking that the smaller the aquarium the easier it will be. Actually, the larger the aquarium is the more stable it will be and the easier it will be to maintain healthy fish. The amount of oxygen available (which is critical to fish survival) is determined mainly by the amount of surface area of the aquarium (not just the size) since oxygen enters the water primarily at the surface. Although aeration, with an air stone or a power head, seems like it is directly adding oxygen to the water, most of the benefit comes from moving water from the bottom of the aquarium to the surface where oxygen is exchanged for carbon dioxide.

Water movement at the surface also increases oxygenation and will generally increase the stocking capacity as well as the health of the fish. Keep in mind that airstones and powerheads can (and generally will) fail at some time or another so don't overstock an aquarium to the point that your fish will die if the power goes out for a couple of hours! It is almost always more desirable to have a few less fish that are colorful and healthy than to push the limits of the tank and risk loosing some of your fish. Not only are fish happier, but the maintenance is easier!

The larger the aquarium, or the fewer the fish, the greater is your chance of having a successful experience!

3. Filters and Filtration 

    There are three main types of filtration for freshwater aquaria: biological, mechanical, and chemical. 

Utilizing each of these three types of filtration will provide you with the most stable and most easily maintained aquarium. General aquarium filters manufactured today include each of these three main types of filtration in some manner.

     

We will also mention several other methods below, that are more commonly used in reef systems, but that can also be beneficial for fish only systems. 

The three main types of filtration are:

1. Biological Aquarium Filtration:

   This is the most important type of filtration for stability and reduction of toxic wastes.

Nitrification: In any biological environment there will be a production of ammonia from normal respiration (fish release ammonia from their gills) and the breakdown of wastes. Ammonia is toxic to fish and in nature is reduced to nitrite by a bacteria called Nitrosonomas. Nitrite is also poisonous to fish and is further broken down into nitrate by bacteria called Nitrobacter. Nitrate is relatively harmless to fish but is a primary food for plants and algae. Frequent water changes (say 10% every week or two) will control nitrate levels. Collectively the process of turning ammonia to nitrate is called nitrification and is carried out in the presence of oxygen (aerobic conditions).

Denitrification: This is the process where nitrates are converted to nitrogen gas in the absence of oxygen (anaerobic conditions). Denitrification is generally not of concern to the freshwater aquarist unless the control of nitrates is desired.

Sponge filters work by passing water over a highly porous sponge where bacteria are allowed to grow. They are almost purely biological with some mechanical filtration provided by the sponge itself. The sponge should not be cleaned or allowed to dry out because this will kill the nitrifying bacteria. Sponge filters are good for breeding situations where very small fish are at risk of being sucked up by the strong intake currents of canister filters or overflows. They are also good for fish like bubble-eyed goldfish that may be injured by strong intake currents of power or canister filters. Sponge filters can be powerd by air pumps or small water pumps.

Undergravel filters are the most common type of biological filter and work by pulling water down through a bed of gravel at the bottom of the aquarium and pulling it up through the uplift tubes. Reverse flow undergravel filters are set up to pull water from the top of the aquarium by pushing it down the uplift tubes and up through the gravel. Reverse flow filters are slightly more efficient since they take water from the top of the aquarium which contains more oxygen.

Since nitrification is more efficient in the presence of oxygen and the air contains about 20% oxygen, as compared to about 7% oxygen for water, trickle or wet/dry filters were developed in the 1980's which increased the efficiency of biological filters dramatically. They place the bacterial growing medium, filter balls with large surface areas, in the air (usually outside the aquarium) and trickle the water to be filtered over them. Many kinds, sizes, and shapes of trickle filters have been in use since they were introduced. Although many trickle filters are external devices used in a sump or hang on the back type of filters, several manufacturers including the "Sea Clear System II" aquarium contain trickle filters built into the back of the aquarium itself. The problem with trickle filters is they usually produce high levels of nitrate, and so are not often used in reef aquariums or other situations where nitrates are undesireable.

Canister filters have a containers or baskets inside the filter for various filter media. For biological filtration you would fill it with some sort of biological media, such as bio balls. This media will either come with the filter or can be purchased separately. Once the bacteria colony has been established on this media you will not need to remove it or clean it.

Standard Power filters use disposable cartridges that have a floss pad surrounding them. This pad is primarily for mechanical filtration but will also house nitrifying bacteria. The drawback to this as a primary biological filter is when you dispose of the cartridge, you dispose of the bacteria colony as well. Today there are more advanced power filters that include a separate area for biological media. These are usually in the form of a compartment in the filter filled with biological media or an attached external 'bio wheel', a pleated wheel that the water flows over as it is leaving the filter and returning to the aquarium.

2. Mechanical Water Filtration:

    Mechanical filtration is good for keeping the water clear and free of debris!

Mechanical filtration refers to the removal of particulate matter from the aquarium.  Canisters and power filters which force the water through some kind of floss or pleated cartridge are both examples of mechanical filtration. Some canister filters such as the "Hot Magnum" provide one media basket for your choice of mechanical filter media or carbon. Other canister filters have more than one basket for a combination of mechanical, chemical (carbon), and biological filtration. Undergravel filters also act as mechanical filters by trapping debris in the gravel. This is one reason the gravel should be siphoned periodically to remove trapped debris.

Diatomaceous earth filters, commonly available in canister filters, can remove particles as small as 3 microns in size which really 'polishes' the water. They can be used to remove bacteria and algae blooms but generally clog after a short period of time and should not be used on a continuous basis.

3. Chemical Aquarium Filtration

Chemical filters are most useful in getting rid of the yellow color that often develops in aquarium water over time!

Chemical filters are used to remove things that are dissolved in the water, and therefore cannot be removed by mechanical filters. The most common chemical filter is activated carbon, used mostly in canister and power filters, it traps many substances in it's minute pores.

Other chemical media include:

• Ammo-chips for removing ammonia

• Nitra-zorb for removing nitrates

• Phos-zorb for removing phosphates

 Nitrate and phosphate control is usually not needed in freshwater aquariums unless the levels become very high, or there is a continual problem with undesireable algae blooms.

Mini-reef aquariums are the most likely candidates for nitrate and phosphate removers if other means of control don't work.

Note : Many of the common aquarium medications including antibiotics are removed by activated carbon. Therefore activated carbon should not be used when treating the aquarium for disease.

Other aquarium filtration methods:

Foam Fractionators, or protein skimmers

Protein skimmers work by passing a large stream of small bubbles through a column of aquarium water. Many different substances (proteins) will adhere to the surface of the bubbles and be removed from the water in the foam that bubbles from the top.

Skimmers are beneficial because they remove substances before they enter into the nitrification cycle which reduces nitrates and increases oxygenation of the aquarium water. One of the drawbacks to skimmers is that they remove trace elements and iodine which, if needed by any of the aquarium inhabitants, must be replaced periodically. This is not usually an issue in freshwater or saltwater aquariums, but both types can benefit from the use of a protein skimmer.

Ultraviolet sterilization

Ultraviolet sterilization works by passing water through ultraviolet light. If the water is exposed long enough, at a high enough concentration of light, bacteria, algae, and parasites can be destroyed by the light. This is used extensively in ponds to help with algae and green water. Treatment of diseases in aquariums requires the most amount of exposure. The smallest units ( 8-9 watt) are made for tanks up to 50 gallons, while the larger 40 watt units are made for tanks up to 180 gallons. For pond applications, 8 watts per 1000 gallons is needed to kill off algae (green water) but is not effective for disease control.

Ozone

Ozone can be passed through aquarium water to oxidize all forms of organic pollutants and kill many of the same organisms that ultraviolet radiation does. Commonly used in skimmers, one should make certain the materials used are "ozone safe" and that the water is passed through activated carbon before returning it to the aquarium because any residual ozone in the water is extremely toxic to the fish. Ozone is useful mainly in large public aquariums and ponds to keep the water from coloring.

Choosing the Inhabitants

1. Stocking Capacity of a Freshwater System

The first thing you probably want to know is how many fish you can keep in a particular sized aquarium.

The two most common formulas for the amount of fish you can safely keep are:

Simple method: 

Keep one inch (1") of fish for each one (1) gallon of water.
This simple method doesn't take into account the surface area of the water (for oxygenation), the filtration system (for removal of wastes), and the general size of the fish. For instance, a fish that is 6 inches long needs a lot more oxygen than 6 fish that are 1 inch long. In general you should reduce the amount of fish if they are larger, and increase the amount of fish if they are smaller.

Surface method:

Calculate the surface area of the aquarium.Multiply the length of the aquarium times the width of the aquarium (in inches) and divide by 12 to get the number of inches of fish the aquarium can handle.

This surface method takes into account the aquarium shape but not the filtration or the size of the fish. The second formula favors aquariums that are shorter and wider i.e. not 'showtanks' which are taller and skinnier.

Note: Neither formula is for coldwater aquariums! In coldwater aquariums you should keep about 2 1/2 times LESS fish than in a tropical aquarium. This means that the surface area should be divided by 30 to get the number of coldwater fish for a freshwater aquarium.

     

In general the more complicated formulas are not worth the trouble if you don't approach the maximum number of fish calculated by the above formulas. Perhaps if anyone shows interest, we can write more on this later.

2. Community Aquarium? or Species Aquarium?

One of the funnest things about setting up an aquarium is choosing the fish!

You should probably have some idea of what type of fish you want to keep before stocking the tank to avoid problems later. Do some research on each fish before adding them to your aquarium.

Some fish are predatory or aggressive and so should be kept either by themselves, or with other predatory species. Aggressive species include Oscars, Jack Dempseys and many cichlids.
 

Some fish are slow feeders, or are very shy and should be kept by themselves in a species tank. A good example of this is Discus fish.

Maintenance, Care, Feeding

1. Water Quality
    By most accounts freshwater systems need partial water changes on a regular basis.

The recommended water change is to change about 15% per month. Note that this is lower than what is usually recommended for saltwater. In deciding how much and how often you wish to do water changes, keep in mind that for stability, smaller water changes done frequently are best. The main reason for water changes is to remove compounds that are not removed by any of the filtration methods such as nitrates and phosphates. Water changes also serve to replenish trace elements, and to clean the gravel of accumulated detritus and waste. Any activated carbon you are using should be replaced monthly.

 

2. Feeding
    Make sure and find out any special feeding requirements your fish may have before purchasing them and be sure you can provide them what they need!

In any case, get your fish to eat as many different kinds of food as you can to ensure they are getting everything they need. Some fish are used to eating all the time so they should be fed as often as is practical (always small amounts at least once per day) while others, like eels can go for several days without food at all. The more you feed your fish the faster they will grow to their maximum sizes.

Important Things You Must Know

1. Obtain as large an aquarium as possible.

2. Purchase the following aquarium set-up components. 

• For filtration we recommend an undergravel filter for both stability and ease of maintenance. Provide a minimum of 2 inches of some kind of non-calcerous gravel on top of the undergravel filter.

• Buy a thermostatic heater, thermometer, and either a good air pump with airline tubing, or a powerhead that pumps at least 3 times as much water per hour as the size of the aquarium. 

• Make sure you purchase some kind of a water conditioner that removes chlorine unless you know there can be no chlorine added to the water. It is better to be safe than sorry in this situation. 

• Purchase test kits for ammonia and nitrite (minimum). 

• Now is also a good time to buy any ornaments that meet your fancy.

3. Set up the aquarium on a sturdy floor in a draft free area 

• Put the undergravel filter in place with either the air stones or the powerheads in the uplift tubes.

• Rinse the substrate material thoroughly before placing it on top of the undergravel filter. 

• Fill the aquarium with water, be sure you treat it with a chlorine remover. 

• Place the heater, ornaments, thermometer, and any lights in or on the aquarium.

4. Run the aquarium for several hours.

• Let the aquarium 'run' for at least a few hours, preferably 12-24 hours, so the water is oxygenated and the temperature is stabilized.
  

 5. Cycle the aquarium and then added fishes.

• Three methods of cycling the aquarium are described here, see Cycling of the Aquarium.

• You must monitor the ammonia and nitrite levels, using test kits, until they are both zero (or very close to zero). During this period (called the nitrification cycle) the ammonia will peak first then drop off as the nitrite peaks, then the nitrite will drop off to complete the cycle. The aquarium is cycled when they are at zero and that will indicate when it is safe to add fish.Don't add fish in the middle of this process. The initial fish will have a good chance of surviving because the levels go up gradually instead of all at once, so they are able to adapt to these changes. 

• After about six weeks, when the aquarium has "cycled", it will be safe to add additional fish. This is indicated by the levels of ammonia and nitrite having drop to zero. 

• Add new fish slowly and keep an eye on the ammonia and nitrite levels to make sure the aquarium is stable.