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My fish are sick!

The Nitrogen Cycle, A Beginner’s Guide......

Without doubt, the nitrogen cycle is the single most important thing you need to learn as a fishkeeper. It is the basis for every form of fishkeeping known to the hobby. A misunderstanding of the nitrogen cycle will ultimately result in sick and dying fish.

It doesn’t matter if you keep marine fish, a community tank, discus, African Cichlids, South American Cichlids, specimen tanks, planted aquaria or a couple of small fish in a nano tank. The nitrogen cycle is the process that keeps them all alive.

Whilst it may appear daunting at first, there will become a moment where it all just falls into place and makes absolute perfect sense.

What is the Nitrogen Cycle?

In simple terms, it’s the process of removing the toxic waste made by fish and by other sources of decaying matter and turning it into a much less toxic form.

What is the toxic waste?

The toxic waste is Ammonia (NH3). Fish produce ammonia from their waste and from respiration and dump it into the water via their gills. Decaying matter, such as uneaten food, dead fish and rotting plants, also produce toxic ammonia.

How is Ammonia removed?

Ammonia (NH3) is converted into less toxic Nitrite (NO2) by the beneficial bacteria living in your aquarium. The bacteria that perform this process are Nitrosomonas bacteria.

Nitrite (NO2), whilst less toxic than ammonia is still toxic to your fish, and also needs to be removed. Another set of beneficial bacteria, Nitrobacter perform this task and convert it into the relatively non-toxic, Nitrate (NO3). If Ammonia and Nitrites aren't removed, your fish will become very sick and ultimately you will experience losses. Poor water quality is the biggest killer of fish we experience in fishkeeping.

How are Nitrates Removed?

As we can see, the end result of the nitrogen cycle is Nitrate. Nitrates are then removed by performing regular water changes. A further method of nitrate removal is from aquatic plants. Plants consume nitrates.

Where do these Beneficial Bacteria Live? The beneficial bacteria that perform the nitrogen cycle live in your filter. You’ll often hear the term “biological filter”. That’s exactly what’s being described here, the biological filter is where the Nitrosomonas and Nitrobacter beneficial bacteria live. Your dealer will advise you not to rinse the biological section of your filter under the tap when cleaning it. This is to avoid the possibility that some of the bacteria may be killed off by the chlorine in the tap water.

How Do I Know if I have Ammonia, Nitrates or Nitrites in my Tank? Test kits are available to buy in store. They are simple to use and will read your water quality in a matter of seconds.

A Happy Aquarium

Once you fully understand the Nitrogen Cycle, fishkeeping takes on a whole new meaning and the once frustrating losses will turn into a thriving, happy aquarium

Please pop in and see us anytime. We are one of, if not the oldest aquatics store in Leicester. We have staff who are formally qualified in all aspects of fishkeeping and fish health.

Friends In Soggy Homes: 0116 267 1661


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