Fish Tank Chemistry 101: Freshwater Aquarium pH

Fishes don’t actually live in waters that are too static, inert or free of anything but just pure water itself; they live in environments that having changing levels of acidity and alkalinity, often known as the pH levels of water.

Now, don’t get confused: although it is termed as acidic, it’s not your stereotypical green oozing liquid that melts anything that it touches.

Acidic in chemistry terms is just the rate of how high is the concentration of hydrogen ions (H+) in a solution after being dissolved in water, which is basically the exact opposite of alkalinity which is determined by the number of hydroxide atoms (OH-).

pH levels in a Fish Tank

Water pH is the general measurement unit for testing the acidity or alkalinity of water. For acidity, anything that is less than 7.0pH is considered as acidic, while anything greater than 7.0pH would be considered alkaline. It is important to know the exact measurements of your fish tank water’s pH and to research about your fish’ pH level tolerance. Neglect of these important variables can potentially cause your fish’s early death.

Measuring pH levels

There are a number of available pH level test kits out there in the market, although it’s still up to the hobbyist on how to use the testing kit properly. Some hobbyists have the tendency to use the pH test kits on tap water right away, without considering the fact that the pH levels of that tap water can change considerably upon use as water in your fish tank. So, you have to test first the water by putting some rocks and gravel into it, and leaving it for about 24-48 hours (leaving the water for a week before testing  works best, although it is indeed a bit time consuming). Then, test the pH levels afterwards, and see if there is any significant change in the water.

Consistency is the Key

For fish, it is vital that you keep the pH levels at a constant rate. They are most likely to get stressed by changing pH levels (for example, a water pH level that constantly shifts from 6.6 to 7.0) even if it’s suitable for the fish’s pH tolerance levels.

This doesn’t mean that you should get it at and exact constant rate, though that would be very difficult. Just keep it at a very low pH swing rate, something at around 0.2 unit change in pH levels should already be tolerable enough for your fish.

Changing the Water pH levels

Usually, the dissolved minerals in the rocks and gravel that you use in your substrate would already provide the right pH that you need for your aquarium, but there are other several methods to manually manipulate your freshwater aquarium pH levels.

Water has a property that is called the buffering capacity, which is the ability to resist any change in pH levels. You should take note of this very well, because even if you put additives in the water to change its pH levels, you might end up as if you did not put the additive at all, because of the high buffering capacity of the water that you are using.

The most common method to increase the water pH levels is to add crushed coral to your substrate. The coral’s composition reacts to the water, and subsequently raises the water’s pH level and maintains it at a certain rate.

Remember that pH levels constantly drop over time, so changing the water periodically is necessary to maintain the pH levels at a constant rate. Alternatively, there are available buffers in the market that can raise the pH levels of your fish tank, but beware of using them in large amounts unintentionally.

If you want to lower your freshwater aquarium pH levels however, then there are also several steps and measures to do so. One is to increase the carbon dioxide levels of the water.

Don’t add too much, just enough for the pH levels to tip off and go over the lower pH zone. Synthetic Chemicals that lower pH levels are also available, but like always, you should be wary of the amount that you are administering in your fish tank.

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