# Nitrate and pH in a Fishlessly-cycled Aquarium

• Frank Pike
In summary, prior to introducing livestock, a fishkeeper can establish colonies of nitrosifying and nitrifying bacteria by repeatedly adding ammonia to an aquarium. This process results in a high concentration of nitrate in the water, typically around 80mg/l. The question is raised whether such a concentration of nitrate can lower the pH, and if so, what type of nitrate would be present. It is noted that cations such as calcium and magnesium are typically present in tap water, and the pH of the resulting nitrate solution would depend on which cation is dominant. It is also suggested that if there is not enough buffer (such as bicarbonate) to neutralize the extra H+ ions produced, the water could become
Frank Pike

## Homework Statement

Prior to introducing livestock, a fishkeeper may establish colonies of nitrosifying and nitrifying bacteria by repeatedly inoculating an aquarium with a solution of ammonia (to simulate the presence of fish). At the end of the process there is a high concentration of nitrate in the water - typically of the order of 80mg/l.

May such a concentration of nitrate lower pH?

## Homework Equations

[none understood]

## The Attempt at a Solution

And anyway, what kind(s) of nitrate is it? Cations can come only from the virgin water (usually tapwater) in which there is typically a preponderance of calcium and magnesium. Is calcium nitrate more likely than magnesium nitrate? I have read that the former's pH is around 4 or 5 ; while the latter's is around neutral. So if calcium nitrate forms there'll be a heap of extra H+ ions around ...

... which is fine so long as there's sufficient buffer (in the form of bicarbonate) to soak them up. If not, then presumably high nitrate in low-buffered water would indeed tend to acidify? Would nitric acid form?

Or am I on the wrong track altogether?

The only thing I can think of is that oxidation of ammonia can acidify the solution:

NH3 + 2O2 -> HNO3 + H2O

You don't produce calcium or magnesium nitrate, these cations were in water and they are still there, nothing have changed.

## 1. What is the significance of nitrate and pH levels in a fishless-cycled aquarium?

Nitrate and pH levels are important factors to monitor in a fishless-cycled aquarium as they can affect the overall health and well-being of the aquatic environment. Nitrate is a byproduct of the breakdown of ammonia and nitrite by beneficial bacteria, and high levels can be harmful to fish and other aquatic organisms. pH, on the other hand, measures the acidity or alkalinity of the water and can impact the fish's ability to regulate their bodily functions. Maintaining proper nitrate and pH levels is crucial for a successful aquarium ecosystem.

## 2. How do nitrate and pH levels impact the nitrogen cycle in a fishless-cycled aquarium?

Nitrate and pH levels are closely related to the nitrogen cycle in a fishless-cycled aquarium. As mentioned before, nitrate is a byproduct of the breakdown of ammonia and nitrite by beneficial bacteria. These bacteria thrive in a specific pH range, and any drastic changes in pH levels can disrupt their ability to process ammonia and nitrite effectively. Therefore, monitoring and maintaining proper nitrate and pH levels is crucial for a healthy and stable nitrogen cycle.

## 3. What are the ideal levels of nitrate and pH in a fishless-cycled aquarium?

The ideal nitrate level in a fishless-cycled aquarium is below 40 ppm (parts per million). Higher levels can cause stress and health issues in fish. As for pH, it is recommended to maintain a range between 6.5-7.5 for most freshwater fish. However, it is essential to research the specific needs of the fish species in your aquarium, as some may require a higher or lower pH level.

## 4. How can I control and adjust nitrate and pH levels in a fishless-cycled aquarium?

There are several ways to control and adjust nitrate and pH levels in a fishless-cycled aquarium. Regular water changes can help reduce nitrate levels, as well as adding live plants that can absorb nitrate as a nutrient. To adjust pH levels, you can use pH buffers or additives specifically designed for aquariums. It is essential to monitor levels regularly and make gradual changes to avoid shocking the aquarium inhabitants.

## 5. Can high nitrate and pH levels be harmful to beneficial bacteria in a fishless-cycled aquarium?

Yes, high nitrate and pH levels can be harmful to beneficial bacteria in a fishless-cycled aquarium. Beneficial bacteria play a crucial role in the nitrogen cycle, and any drastic changes in their environment can disrupt their ability to function. Therefore, it is essential to maintain stable and appropriate nitrate and pH levels to ensure the health and well-being of both the bacteria and the aquatic organisms in the aquarium.

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