Potential hydrogen, often called pH, is a measurement of acidity. A substance with a measurement of 0 to 6.9 pH is acidic, while a pH of 7.1 to 14 is considered alkaline. Most aquarium fish thrive in pure water, which is a neutral pH of 7. A tank with high pH, meaning it's very alkaline, is dangerous for fish and their habitat. If your fish are showing symptoms of illness, check your pH.
One of the most obvious signs that your aquarium's pH is too high is that the fish are behaving unusually. Fish suffering from alkalosis (illness caused by high pH) will exhibit excessive excitement, swimming quickly and chaotically. Some may try to jump out of the tank or purposefully scratch themselves on rocks in the aquarium. Fins will be spread wide, and the gills may secrete mucus. The fish may also appear sluggish and their breathing may be labored.
The aquarium itself will often reveal signs of high alkalinity as well. You may notice a sudden increase in green algae growth on the walls and ornaments in the tank. High pH levels encourage the growth of this algae and slime, which will thickly coat the plants and fixtures, making the water highly toxic for fish.
Symptoms of Disease
Diseased fish are an advanced symptom of high pH. Elevated levels of alkaline often lead to ich (also known as ick), a dangerous disease that can lead to death when left untreated. Fish with ich display tiny white spots all over their bodies. Infected fish will often scratch themselves against rocks or ornaments and may appear very lethargic. Their fins may also develop bloody streaks.
Changing Your Aquarium's pH
If you observe these symptoms in your aquarium and testing reveals pH levels to be high, you must slowly bring the ecosystem back into balance over the course of a few weeks. A rapid change in pH is even more harmful to fish than elevated pH levels, and may result in organ failure and consequential death. Many products are available over the counter for raising or lowering pH: always follow the label's instructions to the letter, and don't adjust your tank by more than 0.3 units of pH per day. A slow changes gives your tank's inhabitants time to adjust.
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