The Nitrogen Cycle of a Freshwater Tropical Fish Aquarium

Now that the tank is running smoothly, and the temperature should be around seventy-eight degrees. I would suggest adding two products that I use in my tank to aid in the breakdown of waste and improve cycling. They are called "Cycle" and "Waste Control" from Hagen. I have been using them since day one and they work wonders. OK time to use our test kit to test several components of your aquarium water. We will test the "PH", "Nitrites", "Nitrates", "Ammonia", "Iron", "Phosphate", "Carbonate Hardness" and "General Hardness". There are several different test chemicals out there but I use the Hagen test kits and find them very reliable. You're saying to yourself, I don't have any fish in the tank, why test the water. The simple answer is we need to know where the water is because in order to get a nitrogen cycle going and for it to complete a cycle, fish need to be introduced. Before we go on I will take the time to explain what a nitrogen cycle is. Nitrogen cycles happen continuously in nature on it's own, but in a Freshwater Tropical Fish Aquarium ecosystem we need to control it.

In stage one, ammonia is produced in the aquarium via tropical fish waste, dead plants and uneaten food. This waste will break down into either ammonium (NH4) or ammonia (NH3). Ammonium is not harmful to tropical fish but ammonia is. If the PH is under seven, you will have ammonium. If the PH is seven or higher you will have ammonia. Most home aquariums unless they are home to fish that need low PH will be above seven

In stage two, bacteria called nitrosomonas will develop and they will oxidize the ammonia in the tank, essentially eliminating it. The byproduct of ammonia oxidation is Nitrites. Nitrites are just as toxic to tropical fish as ammonia.

In stage three, Bacteria called nitrobacter will develop and convert the nitrites into Nitrates. Nitrates are not as harmful to tropical fish as ammonia or nitrites, but nitrate is still harmful in large amounts. The quickest way to rid your aquarium of nitrates is to perform partial water changes.

A new Freshwater Tropical Fish Aquarium without anything in it will not start a nitrogen cycle on it's own. There are several ways to start a cycle but since this is a new setup I will will discuss the first two. The safest and least expensive method is to add a few flakes of fish food every twelve hours. This replicates uneaten food which will decay and become ammonia and the cycle begins. The downside to this is approximately two more weeks without any fish. The second way and the one I have used is to add fish. I started with six neon tetra and a couple silver-tip tetra. Danios are hardy as well. This is quicker but remember ammonia and nitrites are deadly to fish and this can kill them. Daily water tests must be conducted and water changes preformed if the levels climb to high.

Water testing is a very important part of having a freshwater tropical fish aquarium. If we don't know what the water is doing we will not know why we have cloudy water, our plants and fish die or maybe algae is growing. Earlier in the article I listed the main items that needed to be tested for. I will now give you the range that each should be on average for a community tank.

• The PH of my tank is generally in the range of 7.0 to 7.6. It is more important to have a constant PH rather than the so-called ideal PH.

• Nitrites should be kept below .3 mg/L. Nitrites are toxic to fish so if the nitrites climb above this level do a minimum 20% water change.

• Ammonia should be kept below 1.2 mg/L. If the level is above this mark follow the instructions in the test kit to determine the level of toxic ammonia and if a water change is necessary.

• Nitrate levels should not climb above 50mg/L. Levels above this will contribute to the growth of algae. I try to keep my levels around 25 mg/L as this supplies the plants with food but not enough for algae growth. There's a fine line between the the balance of nitrates with the number of plants in the tank.

• Phosphate levels should remain below 1.0 mg/L. Phosphates are a result of poor maintenance or overfeeding. If the levels climb above 1.0 mg/L do a 20% water change.

• Iron levels should be kept as close to .1 mg/L as possible. Iron is a necessary element if you have live plants in your freshwater tropical fish aquarium. A lack of iron will result in poor plant growth and even plants dieing. Excessive levels of iron on the other hand is toxic to fish. A case where more is not better.

• Carbonate hardness should be kept at or slightly above, 80 mg/L. Carbonate hardness (commonly called alkalinity) is the capacity for the water to neutralize an acid. I maintain a level of 80 - 90 mg/L.

• General Hardness is the hardness of your water. A level of 40 - 80 ppm with give you a slightly hard water which I find works great in my community tank.

We now wait until the first cycle completes and the tank settles in and we are ready to start maintaining our tank. I will discuss this in my article titled Maintaining a Freshwater Tropical Fish Aquarium

Live Plants in a Freshwater Tropical Fish Aquarium

Stocking your freshwater tropical fish aquarium with live plants is a very good idea. This will give your tank a more natural look and an ever changing landscape as they grow. Live plants use the nitrates produced from left over food, fish excrement, along with decaying plants and fish that have died and were not removed from the tank.

Deciding if you will be using real plants should be done before you lay down your gravel bed. The reason for this is you will be placing a layer of clay substrate material in your tank. Substrate is the area that the plants will acquire their nutrients from, just like regular plants get their nutrients from the soil. Before adding the gravel or accessories to the tank they need to be rinsed off. I usually rinse everything under the tap with cool or warm water. Soap or other cleaning agents are not needed and can add toxins to your tank if not totally removed. There are several choices for the substrate but one of the easiest is Flourite. Start by placing about 1/2" of gravel on the bottom of the tank and then add approximately 1" of Flourite, and than another 1/2" of gravel. A product like Flourite is a porous clay material that enhances the plants ability to use the nitrates in your freshwater tropical fish aquarium.


OK, now we can start adding any decorations you may want to use. Place them in the tank, visualizing where you will want your plants to be. Place a saucer or plate on the gravel bed and begin filling the tank by pouring the water onto the plate. This will keep the stream of water from disturbing the gravel and stirring up the gravel. You will want to fill about a third of your tank and than add your plants. When planting a stem plant, first cut an angled cut just above one of the healthy green nodes leaving as much of the plant as possible. Now gently push the plant about half depth of the gravel. Remember to space them out as over crowding them will inhibit the lower leaves from getting enough light. Continue filling the tank and than remove the plate. Now that your tank is full, the next step is to get the water circulating and warmed up, and begin cycling your freshwater tropical fish aquarium. Replace the cover and light, than check to be sure that the heater and filter are plugged into the non-timed side of the power bar and the light on the timer side. Plug the power bar into a wall outlet and than set the timer for twelve to fourteen hours. This is the the optimal time that a freshwater tropical fish aquarium should get light. Light is not a factor for the fish but it plays a big part in plant growth and the control of algae. To little light and the plants will not grow or even die, but with too much light algae will grow out of control. I will discuss algae and other maintenance tasks in future articles.

Setting Up a Freshwater Tropical Fish Aquarium

Now that you have decided what size of tank you what and picked up everything you need to get started we can continue setting up your freshwater tropical fish aquarium.

The first thing you will want to do is place the stand in your chosen location. Remember you want it where it can be seen and appreciated completely but not in direct sunlight. You will want to keep the tank about six to eight inches from the wall to allow for the pump, electrical cords and the ability to access the back of the tank. After you have the stand in place insure that it is level. Place your tank on the stand and double check that everything is level. Start setting up your freshwater tropical fish aquarium by placing the gravel(wash with cool water first}and shape it into the look you like. I found by creating a gradual rise of the gravel level from front to back your tank will look deeper from front to back.



The next step is add your decorations and plants, plastic or live. I recommend using live plants as they help to keep your tank clean and healthy. If you decide to use live plants I will discuss the steps to setting up your tank for live plants in the post called Live Plants in a Freshwater Tropical Fish Aquarium. There is no hard and fast rule about accessories, decorations, rocks, plants or other items you may want in your tank, other than they must not be toxic or have the ability to leech toxins into the tank. This is where you can let your imagination go to work. If a week or two later you don't like the look you can rearrange it and give your aquarium a new look.

OK, your tank is the way you want it to look. Place a saucer or any small plate on the gravel. We will pour the water onto this so as not to disturb the gravel, or decorations. Stirring up the gravel also adds to the initial cloudiness of the water. Water that is added to an aquarium needs to be conditioned to remove chlorine and other chemicals toxic to fish. I use a product called Aqua Plus. Fill the tank approximately one third full and than have a look and see if everything looks good. Your aquascaping is the way you want it and this is also a good time to check for leaks, seldom happens but better to be safe than sorry. If you are using live plants this is the time to place them in the tank. I explain this process in my article titled Live Plants in a Freshwater Tropical Fish Aquarium. If everything is in place and looking good, you can finish filling the tank.

Now that your tank is full, the next step is to get the water circulating and warmed up. Check to be sure that the heater and filter are plugged into the non timed side of the power bar and the light on the timer side. Plug the power bar into a wall outlet and than set the timer for twelve to fourteen hours. This is the the optimal time that the aquarium should get light.

Now that everything is running we need to just let the system run as is. I usually let it run for about five to seven days to let the water warm up and clear. In the meantime you may want to order a basic water test kit. We are going to have to make sure the water is safe for the new inhabitants. We will talk about water tests in my article called The Nitrogen Cycle of a Freshwater Tropical Fish Aquarium.