The nitrogen cycle starts because when bacteria generated by the fish you introduce to the tank starts breaking down ammonia, also generated by the fish, and turns it into nitrogen. This can take anything from 24 hours to four weeks before the cycle started.

There is a basic principle to the nitrogen system and you must have this in place before introducing lots of fish. Your aquarium should be set up correctly before introducing any fish to the tank. The tank and substrate should be washed thoroughly in water also any rocks or other objects you are adding to the tank. Soap should not be used. The tank should be filled with water and if it is tap water it should be de-chlorified. Filters and lighting should be added and turned on. The tank should be allowed to cycle through the filters until the water is clear and the correct ph levels and water temperature have been established for the type of fish you are going to introduce.

The basic nitrogen system starts only after the first fish are introduced. The fish need to eat and you have to introduce fish food into the tank. Some of the food which is not eaten will breakdown along with any plant debris like dead leaves, and this turns into ammonia in the aquarium. The fish also generate waste which also turns into ammonia and other toxic chemicals. These chemicals/ammonia need to be broken down or else they would kill the fish. The new fish also generate a good type of bacteria which breaks down the ammonia and converts it into nitrites. These nitrites are not toxic and are beneficial to the fish and other aquatic life you may have in your tank. the nitrates eventually accumulate in the tank are the tanks filter will remove some of them but regular changing of the water should be carried out to remove any large concentrations of the nitrites.

So only introduce enough fish to start the nitrogen cycle. You should purchase hardy fish which can withstand high nitrate and ammonia levels in the new aquarium. Good hardy fish you can start with include gouramis, danios, barbs and live bearers. You should only introduce three or four fish at a time. To acclimatise the fish to the water temperature you should float the plastic bag the come in on top of the aquarium. The temperature of the bag will slowly change to that of the aquarium then you can remove them and place them in the tank. Make sure that the water in the bag does not go into the aquarium it could be contaminated or alter the tanks ph level. Let the fish get to know the tank for a couple of hours before giving them there first feed.

When feeding the new fish you should only give them enough food that can be consumed. Generally if it is not eaten in the first two to five minutes then any extra is not necessary. One of the worst things that you can do is over feed your fish. Any uneaten fish will lodge in the substrate and start to rot. This will increase the chemical levels in the tank. New aquarium owners often over feed the fish but this can be avoided if you monitor how much they eat for the first couple of weeks. And the problem of over feeding is made especially worse in new aquariums because the nitrogen cycle is not properly established. A few other things to do in a new aquarium include testing the ph levels on a daily basis for the first month or so and watch out for the water going cloudy. If this happens you may have to add a water clarifier. The new fish should be monitored for a while for signs of stress or disease. Disease will quickly spread to other fish so if you suspect any fish is diseased it should be removed from the tank and quarantined for a period of time. Things to look out for are: - is the fish swimming regularly, do the fish look lethargic? Lethargic fish can usually be found hovering near the surface of the water. Change about 10% of the water after the first week and then start a regular maintenance system. You can either read up or take advice from your local aquatic pet store expert on this. If you start off correctly you should have an eye catching aquarium to enjoy for years to come.