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Fish Aquarium Cycle

The fish aquarium cycle is vitally important when you're setting up your new fish tank.

In simple terms - it's the process by which beneficial bacteria, break down harmful waste such as ammonia, into less harmful substances called Nitrites, which are then broken down by more good bacteria, into Nitrates in which the underwater plants absorb, which then produce oxygen for the fish to breathe and swim happily. 

Luckily, most fish species are hardy creatures, yet there is only so much of their own waste that they can handle!

In an aquarium they swim around in the same water that they leave their waste in and to keep fish healthy – and alive – it is important to go through a process called the fish aquarium cycle.

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Top 3 Mistakes Newbies Make Setting Up Their Fish Tank.


The Aquarium CycleThe Aquarium Cycle

Everyone knows there are a few critical elements to an aquarium. These include the heater and the light, yet the most important part is the filter.

Its job is to remove the harmful waste from the water so that fish do not get sick. The filter needs to be conditioned by the fish aquarium cycle in order to do its job properly.

This is really all about bacteria. A brand new out-of-the-box filter will be clean and bacteria-free however, bacteria are needed to break down the toxins in the water so that they are not harmful to fish.

Here is the process that takes place in a cycling tank:

  • Waste – The fish eats and then goes secretes waste.
  • Ammonia – Toxic ammonia is created by the waste. This is the chemical that is most harmful to fish and the very compound that a tank, which has not been cycled cannot deal with.
  • Nitrites NO2 – The bacteria in a tank that has been through an aquarium cycle breaks the ammonia down to this less toxic substance.
  • Nitrate NO3 – The bacteria then further breaks this substance down into an even less toxic substance, which fish can live with until the water is changed.

The process of cycling a tank is all about adding bacteria that can then break down toxic ammonia into a less toxic substance.

Fish Aquarium Cycle Hints And Tips

  • Stock Slowly – Except for the hardiest of fish, keep them out of the tank until ammonia and nitrite levels are at zero. Hardy fish that can be added at the start of the process include tetras, barbs and guppies.
  • Filter Media – The easiest way to cycle your new aquarium, is to use filter media from an existing fish tank. This will already have the bacteria colonies you need and will get your new tank started.
  • Other Previously Used Items – Other items out of an existing tank can also be of help, such as gravel, tank decorations and plants.
  • Fishless Cycling – Ammonia needs to be produced for the cycling tank process to work. This is normally achieved by a low number of hardy fish, as mention above. There is an alternative though. Off-the-shelf ammonia can be used in the process.
  • Test Regularly – Ammonia and nitrate level checks should be done regularly.
  • Add Fish Slowly – Do not add fish to the tank too quickly as the bacteria may get overwhelmed if there is too much waste and it will stop working.

Going through a fish aquarium cycle is a process that can take several weeks.

It is also a process that needs great care and attention.

It is critical for any new aquarium. There is nothing more disappointing than seeing your fish become distressed or die because of toxins in the water and just a little bit of effort before the fish are added to your tank can pay big – rather priceless dividends.

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