Freshwater Aquarium Setup - Why Is A New Aquarium So Dangerous To Fish?

When you have just setup your aquarium for the first time you may not realise it but you have created a fish killer. If you introduce your fish immediately you are potentially going to put them through an extremely stressful period which will make them more susceptible to disease and could even kill them.

The reason is because the aquarium has not started to 'cycle' yet. Aquarium cycling has several other names it is also called 'start-up cycle', 'new tank syndrome', 'nitrification cycle', 'nitrogen cycle' or 'biological cycle'.

In a new tank ammonia, produced from fish waste and excess food, builds up to a high concentration in the tank water. This is poisonous to the fish and if it was allowed to continue it would kill all of them. Happily the presence of the ammonia prompts the growth of a particular kind of bacteria (Nitrosonomos) which converts the toxic ammonia into nitrites. That's not the end of the story because nitrites are equally toxic to your fish. So it's a good job that the nitrite causes other bacteria to grow (Nitrospira and Nitrobacter) which convert the nitrite into much less toxic nitrate. We remove the nitrate by changing some of the aquarium water every couple of weeks.

Aquarium cycling is the name given to the above process where ammonia is converted to nitrite and nitrite is converted into nitrate. The problem is, it takes time for this cycle to be established in a new aquarium. The ammonia has to build up to a certain level in order for the good bacteria to grow that convert ammonia to nitrites. Similarly the nitrites have to be present in order for the bacteria to develop which convert the nitrites into nitrates.

In fact, the process can take anything from a week to 2 months to initiate. During that time toxic ammonia and nitrites are building up in the tank. So this is something that needs to happen quickly and preferably with minimum impact on your fish.

The old method of dealing with this was to put a few hardy fish into the new tank and let them go through the cycling process. This is not now considered the preferred method because it is basically cruel to the fish. The fish are sometimes referred to as suicide, starter or disposable fish. Zebra dannios were often used because they are very hardy fish.

The modern way is to do 'fishless cycling'. To create the ammonia fish food can be added to the tank usually every 12 hours or raw fish or shrimp can be added or even pure ammonia can be dropped into the tank. Any of these methods will produce the ammonia which will kick start the cycling. The process can be monitored with standard test strips available from most aquarium shops.

First of all the ammonia levels will go up. Then they begin to fall as the nitrite levels rise. Finally the nitrite levels fall as the nitrate levels rise. This is when you need to start changing the water (about ¼ to 1/3 every two weeks) and it is also the time you can add your fish to the tank.

Products are available that can speed up the whole process by introducing the good bacteria.

So there you are. Avoid the biggest beginners' mistake. Make sure your new tank is cycling before you think of adding any fish.

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John Thomson is an aquarium expert. For more information on freshwater aquarium setup, visit http://www.freshwateraquariumsecretsonline.com