Looking at a crystal-clear fish tank is very peaceful and relaxing.  But it does not start out that way.  To be able to keep fish in a glass box, there is a lot of science going on in the background.  I am going to explain how the cycling of an aquarium works and what is happening for fish and other inhabitants to live a healthy life. Have you asked yourself “Why is my aquarium cloudy?”

Fish produce waste which gets broken down as ammonia.  In a new aquarium there is not any bacteria to eat this waste, so a bacterium called Nitrosomonas begins to form and multiply to consume ammonia into another form, called nitrite.  Ammonia and nitrite are very toxic to fish, and in order for nitrite to be removed from the aquarium, a second bacteria called Nitrobacter starts to reproduce and consume the nitrite, turning it into a less toxic chemical called nitrate. 

While all these bacteria are growing and consuming its respective foods, you are likely to see a bacterial bloom or cloudy water.  First ammonia will spike, causing milky looking water.  Then when enough bacteria are produced ammonia will level out.  Next, nitrite will spike and the bacteria that eats it will increase.  Finally, nitrate will be left, and the bloom will start disappearing.  With regular water changes nitrate gets removed and does not usually affect fish unless it can reach very high levels. 

Source: https://www.aqueon.com/articles/freshwater-aquarium-water-quality

Cycling a tank can take 2-6 weeks.  There are a lot of bacterial products available today that can quick start the nitrogen cycle and reduce the time needed for the cycling progress.  I recommend using a fish free cycling by adding ammonia directly to the aquarium then adding the nitrifying bacteria. This avoids using fish to add ammonia and prevents any deaths or stress to the fish.

Investing in proper filtration will save you headaches in the long run and keep your biological filtration at optimal levels.  You will want to make sure your filter has chemical, biological, and mechanical filtration for best results.  Canister filters are great for this and once set up very efficient. 

To monitor the ammonia, nitrite, and nitrate levels you will need a quality test kit.  By testing at least every week you will be able to see the levels rising and falling and know exactly when your aquarium is ready for fish.  When ammonia and nitrite read zero your aquarium will be cycled and ready for fish to move in! Now you have your answers on “Why is my aquarium cloudy?”

By: John Wright of Wright Aquarium Services