There may be a misconception amongst beginner aquarists about what constitutes high and low pH either due to a lack of knowledge about the pH level system. As we have said in our other articles on pH levels the pH scale ranges from 0 (the most acidic) to 14 (the most alkaline).
‘Raising’ generally means increasing a number from a low one to a high one, and lowering vice versa. This is the exact opposite of the pH scale. Imagine that the pH scale is a literal scale.
In an aquarium, we want our scale to be as balanced as possible, bringing it to the general range of pH five to eight that most species of animals prefer.
Let’s take the tetra fish as an example; they prefer a pH of 5.5 to 7.5. You test your tank and the level reads 4.5; this is approaching a pH level toxic to adult fish! You should add something with a higher pH number, such as limestone (generally pH7.5 to 8) or baking soda (a pH of 9) in small doses over the course of a few days. Baking soda is commonly preferred by people with aquariums because it is very cheap, and easy to purchase and use. It also doesn’t contain any other chemicals that could affect your water, as other additives could.
Use approximately one teaspoon of baking soda per five gallons (nineteen litres) of water to raise your pH level slowly to prevent your fish being affected by a rapid pH change. For more information about how to use baking soda to raise your pH level, check out our article that goes further into the topic.