Maintain the pH Balance in Your Goldfish Pond

What is pH?

H2O splits into two things: a positively charged hydrogen, H+ and the negatively charged hydroxyl, OH-; pH is the measurement of hydrogen ions available in the water. The term ph literally means “power of hydrogen”.

pH Scale

pH is based on a scale from 1-14; one being the most acidic and 14 being the most alkaline. The pH scale is logarithmic which means that for example, a pH of 8 is ten time more alkaline than a pH of seven. A pH level of 7 is neutral and in most cases, most tap water is close to that range, plus or minus .5 pH. Rain water in your tap water system can be the cause of a lower than 7 pH reading and an elevated reading can be the cause of chemically altered water by municipalities in hard water zones.


Your goldfish will thrive in waters with a pH of 7-8.5, neutral to slightly alkaline.

pH Test

You can buy an inexpensive pH test kit at your local pet store. There are a few options when selecting pH test kits: strips, drops or tablets. All of them will give you close to the same readings; the tablets and drops being the more accurate methods but taking a few more minutes to get a reading. There are no real tricks or difficulties in testing your goldfish aquarium’s pH, just read the easy to follow direction on the box of your pH testing kit.


You should test weekly for pH levels.

Low pH: Acidic

Low pH levels are caused by

• Rain water that can contain natural acids.
• Wind blown leaves and other organic material.
• Decaying and dying back aquatic plants.

Symptoms of low pH levels

• Goldfish are listless or slow moving
• Pond snails begin to die off
• Slow growth of aquatic plants

Advanced Symptoms of pH Derangement

• Excess mucus production of goldfish
• Milky skin of goldfish
• Slime coat peals off
• burning of goldfish skin

High pH: Alkaline

High pH levels are caused by

• New goldfish ponds can leach lime out of concrete.
• Concrete dust or particles left in new goldfish pond.
• Excessive algae growth that will consume CO2.

Symptoms of high pH levels

• Slow growth of aquatic plants
• White powdery coating on aquatic plants*

*calcium precipitating found on aquatic plants like Elodea Crispa.

pH Adjustment

Goldfish are sensitive to pH level changes. A fast decrease in pH can kill your goldfish. A fast increase is less harmful but in general, don’t change your goldfish tank’s water more than .5 pH at a time.


To lower your pH, you should make sure you seal any concrete with a aquatic concrete sealer, remove any concrete dust or debris, remove excessive algae growths and blanketweed. Using a water purifier like a Brita or Pur to fill your tank or pond can lower the pH by easily 1 pH level if not more (test it using your pH test kit). If these don’t do the trick, buy a pH adjuster from your local pet store or buy this: Alkaline Buffer

To raise you pH, you should do a regular 20% water change, remove rotting plants and vacuum the bottom of the goldfish tank to remove impurities. If these don’t do the trick, again try buying an alkalinity buffer from your local pet store.




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