top of page

Cycling The Discus Fish Aquarium


The purpose of the filter in the discus fish aquarium is to provide a suitable media for beneficial bacteria to colonize. The aquarium filter bacteria consume discus fish waste products as a food source. This process is referred to as the nitrogen cycle, or nitrification.


Before setting up the discus fish aquarium, test your tap water for carbonate hardness and ph. The aquarium water should be adjusted to the parameters of hardness and ph that you intend to use for the fish. If you attempt to lower the aquarium ph and it keeps bouncing back up within a few hours, the water has high carbonate hardness. If the carbonate hardness is over 120 ppm. consider using reverse osmosis water (ro water) to blend with the tap water to achieve the desired hardness range. Distilled water or deionized water (di water) may also be used to soften water in the discus fish aquarium. Carbonate hardness in the 80 ppm. range makes it easy to adjust the ph of the aquarium using one of the acid buffer products available. Should you choose to raise your discus fish in harder water with a higher ph, it is a good idea to start out in this range and slowly adapt them to the change.

The discus fish aquarium filter should be established with nitrifying bacteria before the introduction of discus. Many good products are on the market to speed up the nitrification process. If an aged filter or filter media is added to the new aquarium, along with water from an existing aquarium, discus fish may be introduced immediately. Remember the nitrifying filter bacteria need the fish byproducts for a food source. Do not add the established filter media to the aquarium in advance of adding the fish or the bacteria will starve. They should both go into the aquarium around the same time.

The most common method used in the aquarium cycle process is using a "hardy" type of fish which can withstand high ammonia levels and high nitrite levels. My friends, being able to withstand high ammonia levels and high nitrite levels does not mean the fish are happy, healthy or that they are not suffering. The fish are removed when the aquarium cycle is complete, prior to adding discus fish. Water is changed and fish are added. The process of the discus fish aquarium cycle can take 3 weeks or longer. Using this method of aquarium cycle you run the risk of introducing pathogens into the aquarium. Also it is not humane to subject fish to the extreme conditions of high ammonia and high nitrite levels  involved in this type of aquarium cycle. Many pet shops will recommend this method of aquarium cycle as it sells a few goldfish or other type of tropical fish. 

A fishless discus fish aquarium cycle can be done by adding ammonia to the aquarium. This method has been around for many years. Twenty years ago hobbyists would throw a handful of flake food into the aquarium. Over time the food would decompose and produce nutrients (ammonia) to get the process started. It was messy but did accomplish the aquarium cycle.


The Fishless Discus Fish

Aquarium Cycle Method


The steps below give details on the fishless method of the aquarium cycle for your discus fish aquarium. This process is done in the absence of any fish in the aquarium.

Fill the discus fish aquarium with dechlorinated water. Set the heater at 88 degrees. DO NOT USE A WATER CONDITIONER THAT REMOVES AMMONIA. 

Add pure cleaning ammonia that does not have any scent or additives in it to the aquarium. Obtain a 5 (five) ppm. level of ammonia in the empty discus fish aquarium. Add either a commercial product having filter bacteria in it or some filter media from a healthy established tank. This provides a starter culture of nitrifying bacteria. Maintain the 5 ppm. ammonia level. In a few days the ammonia level will drop. Nitrite levels will rise. While awaiting the nitrite levels to fall, feeding ammonia at a level of .5 ppm (half of one ppm) every two days is sufficient. When the cycle is completed, you should be able to add ammonia at .5ppm. and see a zero reading within 8 hours. Nitrite levels should not rise. However, nitrate levels will climb indicating a healthy functioning biological filter, or cycled aquarium. Reduce the aquarium temperature to 86 degrees for discus fish. For other type tropical fish adjust the temperature to the appropriate range. The aquarium is now ready for a large water change to remove the nitrates. Fish must be added to supply food for the aquarium filter bacteria. If the cycled aquarium will not have any fish for several days, the bacteria can be fed ammonia. Add a low dose of ammonia and redose when tests indicate zero ammonia. Change water before adding discus fish to the aquarium. 






bottom of page