003: Cycling Your New Freshwater Aquarium

The real heart of any aquarium’s filtration, freshwater or marine, is bacteria. Beneficial bacteria consume and break down the waste products produced by any fish or other animals within the system, namely ammonia. Without them the ammonia levels within the tank can become toxic within days or even hours. The goal of cycling is to establish a healthy colony of beneficial bacteria within the tank to prevent this. Well, actually two colonies: the first to consume the ammonia and convert it to nitrite, and the second to consume the nitrite and turn it into nitrate. Most fish can tolerate nitrate at relatively high levels, although it will need to be removed eventually, typically through water changes. Live plants can also consume nitrate as well as ammonia.


Luckily for aquarists these bacteria are easy to cultivate. They are all around us and if given the right conditions will happily set up shop begin to grow. For your aquarium as it is now the only missing component is a steady supply of ammonia. There are a few ways to achieve this.


Probably the easiest is to start feeding the tank as if it had fish in it already. The unconsumed fish food will begin to decay, releasing ammonia. The disadvantage of this method is that it’s pretty much a guessing game of how much food to add. The ammonia supply released by the food can also be somewhat sporadic since the food is only added at most a few times a day. There’s also the matter of all decaying fish food that’s left over once cycling is complete that will need to be cleaned up. None the less it is a viable and easy method.


An improvement on this method is to use a piece of raw shrimp. You can place the shrimp in a mesh bag (pantyhose work well) and hang it in the tank. It will break down steadily, providing a steady source of ammonia, and once cycling is complete it can be removed easily. As with the fish food method the water quality will be degraded somewhat by the other byproducts of the shrimp’s decomposition, but much less so since the mesh bag should contain it for the most part.


Of course the most direct method for increasing the ammonia levels in your aquarium is to, well, add ammonia. Ammonia can typically be found for sale with the cleaning supplies in most stores. If you decide to go with this method make absolutely certain that product you buy contains no dyes, scents, soaps or other chemicals other than water. Any of these can be fatal to the tank’s future inhabitants. Add it to the tank at a rate of around 3 drops per ten gallons or water on a daily basis. Splitting the dosage up and adding it a few times a day is even better.


Whichever method you choose, regular testing is necessary to know when the cycle is complete. You will need two test kits- one for ammonia and one for nitrite. A nitrate test kit can also be helpful. While paper dip strip style test kits are available for these test, liquid based kits are recommended as they tend to be much more accurate. You’ll want to test the water daily and watch for a spike in first ammonia and then nitrite followed by a gradual drop off in each. This whole process should take a few weeks. Good water movement and oxygenation and higher than normal temperatures can reduce the time required, so run the filters and heater during this process as well.


One final method for helping this process along is to seed your aquarium with the bacteria from an already established system. The beneficial bacteria grow primarily on the surface of anything in the tank, so if you can obtain a decoration, some gravel, or even some used filter media from an established tank it will go a long way towards starting yours. Simply transfer the item into your tank, making sure to keep it wet the entire time. Remember even with a seed of bacteria from an established tank you will still need to provide ammonia for it to grow using one of the methods above.


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