How to fix a pH crash in the aquarium

Today we will be looking at pH & KH (Carbonate Hardness) and the influence they have on aquarium water. Let’s start by talking about water itself: life is not possible without water. That is why scientists at NASA look for signs of water on other planets in our galaxy and beyond, because the presence of water could mean presence of life. Therefore, H₂O is often referred to as 𝘁𝗵𝗲 𝗺𝗼𝗹𝗲𝗰𝘂𝗹𝗲 𝗼𝗳 𝗹𝗶𝗳𝗲, consisting of one oxygen and two hydrogen atoms. Water has an extensive capability to dissolve a variety of molecules, earning it the title of “universal solvent”. It is this ability that makes water an invaluable life-sustaining force. So, let’s take a closer look at various water parameters that are important for fish keeping.

𝗽𝗛
pH is an important value in regards to water quality, it indicates how acidic (sour) or basic (alkaline) water is. The range goes from 0 to 14, with 7 being neutral. A pH of 𝗹𝗲𝘀𝘀 𝘁𝗵𝗮𝗻 𝟳 means the water is 𝗮𝗰𝗶𝗱𝗶𝗰, A pH of 𝗺𝗼𝗿𝗲 𝘁𝗵𝗮𝗻 𝟳 means the water is 𝗯𝗮𝘀𝗶𝗰.

𝘱𝘏 𝘳𝘢𝘯𝘨𝘦: 𝟬 – 𝗔𝗖𝗜𝗗𝗜𝗖 – 𝟳 – 𝗕𝗔𝗦𝗜𝗖 – 𝟭𝟰
𝘈𝘤𝘪𝘥𝘪𝘤 𝘸𝘢𝘵𝘦𝘳 𝘩𝘢𝘴 𝘮𝘰𝘳𝘦 𝘧𝘳𝘦𝘦 𝘩𝘺𝘥𝘳𝘰𝘨𝘦𝘯 𝘪𝘰𝘯𝘴.
𝘉𝘢𝘴𝘪𝘤 𝘸𝘢𝘵𝘦𝘳 𝘩𝘢𝘴 𝘮𝘰𝘳𝘦 𝘧𝘳𝘦𝘦 𝘩𝘺𝘥𝘳𝘰𝘹𝘺𝘭 𝘪𝘰𝘯𝘴.

pH is an important indicator to see if the aquarium water is changing chemically and is indicated by logarithmic units, meaning each number represents a 10-fold change in the acidity / basicity of the water.

𝗔𝗻 𝗲𝘅𝗮𝗺𝗽𝗹𝗲:
pH 5 contains 10 times more acid than pH 6, but pH 9 contains 10 times more base than pH 8! pH 7 is the neutral one, where acid and base are in equilibrium.

So essentially, the pH tells you how acidic or basic your aquarium water is by measuring the amount of hydrogen ions in the water. pH changes naturally throughout the day in an aquarium, mostly driven by variations of the CO2 concentration in the water. It is important to get a relatively stable pH with no sudden changes, up or down. Generally speaking, most freshwater fish do well with a pH between 6.5 and 8.

𝗞𝗛
For a stable pH you need a buffer. The buffer capacity of water is represented by the KH, which measures the number of carbonates and bicarbonates in natural water. KH helps to dampen the influence of extra acid or base and therefore helps in maintaining a stable pH. A low to very low KH can be dangerous because your water will have a low buffer capacity and the pH will shoot up and down due to small changes in the number of acids or bases. When your KH is low and your pH is unstable you could get into the very unfortunate situation of a 𝗽𝗛 𝗰𝗿𝗮𝘀𝗵. If you have tap water with a low KH you can use crushed coral stone, marble or a commercial buffer to slowly raise the KH in order to prevent a pH crash. We measure KH in dKH, degrees of KH or ppm, parts per million: 1dKH = 17,9 ppm CaCO3. In general, a KH between 4 – 8 dKH is great for most freshwater fish. Be aware though, you don’t want your KH to go below 4 dKH, because your pH will become unstable and can crash, which in turn can result in severe damage and even death of your beloved fish. In the pictures you see a fish that suffered from a sudden pH crash, but recovered after a water change and adding crushed coral stone. We would like to emphasize the importance of regular water changes in freshwater aquariums, because over time the KH inside your aquarium will gradually drop when you don’t regularly add new fresh water or unless you have carbonate releasing materials like marble or crushed coral stone, these can cause your KH to rise over time.

𝗽𝗛 𝗰𝗿𝗮𝘀𝗵 𝘀𝘆𝗺𝗽𝘁𝗼𝗺𝘀:
∙ Signs of stress
∙ Swimming frantically
∙ Rapid breathing
∙ Lethargic
∙ Strange, erratic behaviour

In conclusion, if you see anything out of the ordinary, measure the quality of your aquarium water using eSHa Aqua-Quick-Test (look specifically at the KH, pH, NO2 and NO3), perform a water change and diagnose properly and treat the identified problem accordingly.

𝘋𝘪𝘥 𝘺𝘰𝘶 𝘭𝘪𝘬𝘦 𝘵𝘩𝘪𝘴 𝘢𝘳𝘵𝘪𝘤𝘭𝘦? 𝘓𝘦𝘵 𝘶𝘴 𝘬𝘯𝘰𝘸 𝘸𝘩𝘢𝘵 𝘸𝘦 𝘸𝘪𝘭𝘭 𝘥𝘪𝘴𝘤𝘶𝘴𝘴 𝘯𝘦𝘹𝘵!