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How does carbonate hardness affect my pond and fish? | Ponds & Lakes Q&A

How does carbonate hardness affect my pond and fish?

Q: How does carbonate hardness affect my pond and fish?

Bob – Underhill, VT

A: Hard water, soft water – you’re probably familiar with these terms as they relate to the water flowing through your home’s plumbing. But the water in your pond or lake can be hard or soft, too, and it matters to your fish, particularly if you’re using algaecides or herbicides.

A Natural Buffer

The technical term for hard or soft water is “carbonate hardness” and, simply put, it refers to the amount of calcium and magnesium present in the water. The greater the water’s alkalizing mineral content, the harder the water is. Those microscopic minerals actually act as a buffer that offsets swings or dramatic changes in your pond or lake’s pH level caused by chemicals found in algaecides and herbicides.

Fish Friendly

The beneficiaries of the hard water’s buffering calcium and magnesium are your fish. Carbonate hardness in your pond or lake affects the sensitivity of certain fish—mainly trout, koi and goldfish—to the acidifying chemicals found in algaecides and herbicides. If you have high carbonate hardness, or hard water that contains more than 50 ppm of the minerals, the fish are less likely be affected compared to those fish in that are in soft water.

Measuring Minerals

If you’re curious about your water’s carbonate hardness level, or you plan to use an algaecide or herbicide in your lake that requires hardness to be at about 50 ppm, test your water with a Carbonate Hardness Test Strip.

The strips are easy to use. Simply open the pouch and dip it into the water for three seconds, remove it from the water, wait 20 seconds for the water to mix with the solution in the pouch, and remove the strip. To see what your water’s carbonate hardness is, match the color on the strip to the color block on the package.

Remember to perform this test each time before you treat your pond with herbicides or algaecides as the levels of calcium and magnesium in the water may fluctuate.

Pond Talk: How often do you test your lake for carbonate hardness?

Carbonate Hardness Test Strips - Test Your Water Hardness With Ease

What is carbonate hardness and why does it matter? | Pond & Lake Q&A

What is carbonate hardness and why does it matter?

What is carbonate hardness and why does it matter?

Marlena – Richmond, MI

Carbonate hardness is a measure of the amount of calcium and magnesium present in water. As it turns out, these elements are vital to the health and well-being of certain fish – including trout, koi and goldfish – because of their ability to neutralize acids in water and stabilize healthy pH levels.

But why, you might logically ask, are acids a concern? You’ve just asked the sixty-four thousand dollar question. In the course of regular pond maintenance, it’s common to apply algaecides and herbicides. Often, those products contain chemicals that are acidic, and when they’re applied, they can cause pH fluctuations that certain fish are ill-equipped to handle. Thus, water that’s “hard” – or rich in calcium and magnesium – helps to minimize those fluctuations, protecting fish from harm. Other environmental factors, including runoff from fertilized lawns, can have a similar effect on pH, making it all the more important to ensure that your water maintains a safe level of carbonate hardness.

As a rule, algaecides and herbicides indicate a recommended level of carbonate hardness in pond water to ensure that their effects won’t harm fish. Low carbonate hardness is generally indicated when calcium and magnesium levels are below 50 parts per million (ppm). And fortunately, it’s easy to test your water to determine its carbonate hardness levels. With our Carbonate Hardness Test Strips, you can test your water prior to each application of algaecides and herbicides. If levels are above the range indicated on the product you’re planning to use, the pH of the water will be safe for fish even after application.

Pond Talk: Is water hardness a concern where your pond is located?

Carbonate Hardness Test Strips

Why do I need to test for carbonate hardness in my lake or pond? – Pond & Lake Q & A

Testing for Carbonate Hardness

Pond & Lake Q & A

Q: Why do I need to test for carbonate hardness in my lake or pond? – Jose in Michigan

A: A number of pond treatments, including some algae-control formulas and other herbicides, contain copper. In certain conditions, the copper chelate may break down and release copper ions, which could cause your pond or lake’s alkalinity to rise.

If you use these treatments in a pond or lake stocked with trout, koi or goldfish that are sensitive to high alkalinity levels, you need to test your hardness regularly to ensure the health of your fish population.

What is Carbonate Hardness?

Carbonate hardness, or alkalinity, is the measure of carbonate and bicarbonate concentrations in your pond or lake’s water. Alkalinity is a measure of the ability of a solution to neutralize acid without changing the pH. It both controls and maintains water pH.

Alkalinity is related to the amount of dissolved calcium, magnesium and other compounds in the water, so alkalinity tends to be higher in harder water. It naturally decreases over time through bacterial action that produces acidic compounds that combine with and reduce the alkalinity components.

In a pond or lake, the alkalinity of the water is critical to the health of the fish – especially for trout, koi and goldfish. For these fish, the carbonate hardness of your pond or lake must exceed 50 ppm for the fish to survive, ideally falling between 50 ppm and 200 ppm.

Testing 1, 2, 3

When you’re treating your pond with a product like Pond Logic Algae Defense, be sure to use a water hardness test kit, like Laguna Quick Dip Multi-Test Strips.

Carbonate hardness is measured in degrees (KH) or in parts per million (ppm). Because the water hardness test kit will give its results in degrees, you’ll need to convert your findings from KH to ppm to determine whether the levels in your lake are safe for your fish. Use this formula to figure it out: 1 KH = 17.848 ppm. So if your test kit reads 5 KH, you would multiply 5 times 17.848, which equals 89.24 ppm.

POND TALK: How often do you test your pond or lake’s carbonate hardness level?

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