Cycling your aquarium – Water chemistry

Once your aquarium and filter has been installed, you should only add the required bacteria starter culture (available in specialist pet shops) after your aquarium water has reached the required temperature of 29°C / 84°F. From the moment you add the bacteria starter culture, you should begin “feeding the empty aquarium” once daily with a little food. The process of “feeding an empty aquarium” is necessary because it provides the bacteria with nutrients and allows them to multiply. After about two to three weeks, a sufficient bacteria culture for filter performance will have developed in the aquarium and then the aquarium can be stocked with fish. 

Before adding your fish, test the water chemistry in your aquarium. It is important that the test shows no traces of ammonium, ammonia or nitrite, as these are toxic for discus fish. In theory, these contaminants should already have been broken down. The pH value of the water should be between 6.5 and 7.8. To protect your fishes’ fins and mucous
membranes, you can add a water conditioner just prior to adding your fish to the aquarium. Then, you’re finally ready to add your fish. Liquid drop test kits/ indicator kits for pH value, nitrite, nitrate, ammonium, ammonia, etc. are available in specialist pet shops. When you initially “feed” your empty aquarium, nitrite will develop in the aquarium water (can be tested using a liquid drop test kit/ indicator kit). After two to three weeks, the nitrite content will have been broken down and the aquarium water is ready to be stocked with plants and fish. 

Testing your water:

Ammonium develops when the pH value of the water is below 7, or when a filter is not yet functioning fully. You can prevent the ammonium value from rising, by minimising the amount of feed you give your fish.

Ammonia develops when the pH value of the water is over 7. It is toxic and will develop if a filter is not yet functioning fully. You can prevent the ammonia value from rising, by minimising the amount of feed you give your fish. The ammonia level should be 0.0ppm or undetectable.

Nitrite levels should be tested daily in new aquariums. Once you are feeding normal (full) amounts and nitrite traces are no longer present, you can then cease testing for nitrite. Only if the filter performance drops due to filter cleaning or after a filter outage/ failure you need to test for nitrite daily again (for approx. 1 week). This is to check whether the filter has reached its full performance again. You can also tell from the behaviour of your fish, if nitrite levels are extremely high. Generally, the fish start refusing their feed and breathe heavily and quickly. If this is the case, please test for nitrite immediately. If nitrite levels are high, stop feeding immediately and carry out a 90% water change as nitrites should also be at 0ppm or undetectable.

Nitrate levels should be tested three or four times a year, just prior to a water change. If nitrate levels are over 380 mg per 3,8 litre / 1 gallon, it is advisable to change more water and/or carry out water changes more often, to ensure healthy growth for your fish.

Test your pH once a week. If the pH value falls from, say, 7.5 to 6.0 before a full week has passed, then it is already time to carry out your water change. Otherwise the pH value – and hence the acidity of your aquarium water – will drop very quickly. If the pH value reaches 3.6, the acidity is so high that it is lethal for your fish.

Phosphate levels only need to be tested if you observe increased algae growth. You can lower phosphate levels by exchanging more water and/ or carrying out water changes more often.

General hardness
If you mix tap water with osmosis water to keep Wild caught discus fish or to keep breeding discus pairs, you need to test the water mix only at the beginning, to ensure an ideal GH value of between 1 and 4.