How to Make pH Stable at Night, When Lights Are Off in a Reef Tank

Building a reef tank means creating a delicate balance inside a glass tank. In nature, this balance exists most often due to the sheer size of the coral ecosystems and was slowly achieved over a period of decades or centuries. The balance of predators and prey, hosts and symbiotic organisms, but also of nutrients and waste materials. Nature itself strives to achieve it when there are no detrimental factors.

When building a reef tank, it is your goal to create and maintain this balance that will make your tank thrive. After all, the goal of building a reef tank is its beauty that can be achieved only if it is a healthy and thriving ecosystem. To achieve this you will have to monitor and adjust the parameters of the tank water, and one such is its pH value.

Why Does Aquarium pH Drop at Night?

One of the main culprits of decreasing pH value in your aquarium is the increase of Co2. Carbon dioxide is a normal byproduct of the breathing of all living organisms, which includes fish and other marine life. Just like in the land ecosystem, in your tank, this excess Co2 is caught by plants and algae and through photosynthesis is transformed into various carbohydrates and oxygen.

During the night there is no sunlight available for the photosynthetic organisms to transform it, and then there is an increase in the carbon dioxide level in your tank that decreases the pH level of the water. Some fluctuation is of pH level is expected and normal, but pronounced dips of its level are when you need to take actions to make it more stable.

How to Make pH Stable at Night

How to make pH stable at night, when lights are off in a reef tank is a decision you will need to make in case of a pronounced decrease of the pH level. The easiest way to make pH stable at night is to dose alkalinity additives, such as sodium carbonate, during the hours of the night when pH is at its lowest level.

Maintaining the proper alkalinity level of your reef tank is very important for the health of your living rock and corals. The beneficial side effect of adding sodium carbonate is the increase of the pH level of the water, so timing is when pH level should be increased produces a double effect.

How Do I Raise the pH in My Reef Tank Without Increasing Alkalinity?

Dosing the additives for alkalinity can increase the pH level, but it is possible that the conditions of your reef tank are such that they are not a good solution for low pH levels during the night. In such cases running the reverse light-cycle is a much better solution. This will induce photosynthesis in your tank plants and algae, and excessive Co2 will be used for oxygen production.

Lower carbon dioxide levels will increase the pH level of the water, and photosynthesis is the natural process of its transformation in oxygen. Another very simple way to stabilize the pH level of your tank is to keep the air in the room where it is fresh. There is always the exchange of the gasses between the water and air above it.

If your tank is in a living space that lacks proper ventilation it will have an increased level of carbon dioxide. This can be prevented by regularly airing the room in which your tank is located.

Why Does My pH Keep Dropping in My Saltwater Tank?

There are several reasons why pH levels can drop inside your saltwater tank. Normal respiration of all living organisms uses the oxygen from the environment and has carbon dioxide as a waste byproduct. Carbon dioxide dissolved in water increases its acidity, in other words, lowers the pH level of your reef tank water.

Metabolism of all living beings has other waste products too, the organic acids that also increase the pH levels such as the nitric acid. One factor that impacts the pH level that is often ignored is the temperature of the water. With its increase rises the ability of water to ionize, and the increase of hydrogen ions concentration will lower the pH levels.

Will Low pH Kill My Fish?

All marine life has a pH level they have evolved to thrive in and it varies between the species. Too low or too high a pH level is detrimental to their health. If the pH level is lower than the desirable level, the acidity of tank water will first cause chemical burns on fish skin, and if it goes much lower it can even kill them.

The ionizing effects of low pH levels are very dangerous for the skin of fish. But low pH level water is very rich in carbon dioxide and has very low oxygen levels which can lead to fish suffocating.

How Do You Raise pH in an Aquarium?

The pH level of the aquarium is easiest to raise in one of two ways, by adjusting the alkalinity of the water or by stimulating the photosynthesis of scrubbers. The pH level of the water in the aquarium is most commonly low due to carbon dioxide buildup inside of it, and adding the additives that increase the alkalinity will increase the pH level too.

Because the organisms that perform photosynthesis use carbon dioxide as a “fuel” for it, they naturally lower the Co2 level in the water. By using artificial lights to stimulate this natural process they will scrub carbon dioxide from the tank and produce oxygen which is necessary for all living beings in your tank.

What pH Should My Reef Tank Be?

Different marine species prefer different pH levels to thrive and be healthy, and it is important to maintain the pH level in the range which is the best suited for them. Some suggested pH level for the majority of reef aquariums is between 8.1 and 8.4. These levels are closest to their natural habitats and will allow them to be healthy and grow properly.

But pH level is not the only measurement that impacts the health of your reef tank. Temperature, salinity, alkalinity, and calcium and magnesium levels also need to be in the proper range. If they are the ecosystem in your tank will be able to thrive even in a lower pH level environment.


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