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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’s a Nitrogen Cycle? – Decorative Ponds & Water Gardens Q & A

PondCare Master Test Kit - Complete System

Explaining the Nitrogen Cycle

We’ve Got Good Chemistry
Today we trade in our waders for lab coats as we discuss your pond’s nitrogen cycle. While many of us find it hard to stay awake for science lectures, we promise this one will save you time and money and give you the upper hand in the fight against algae and fish kills. The nitrogen cycle is present in all water gardens and is truly a great thing when in balance. As plant matter decays and fish produce waste, ammonia is released into the water. The bacteria in your pond naturally break this ammonia down into nitrites and then down into nitrates. Plants, including algae, feed off of these nitrates, which in turn die and decompose or are eaten by fish and the process repeats itself. Having too many fish in your water garden or an abundance of decomposing organic debris can dramatically increase the amount of ammonia in your pond and, in turn, can harm your fish or turn the water body into an all you can eat buffet for unwanted algae.

Put Your Water Garden to the Test
Different types of test kits are available for purchase that will allow you to measure nitrite levels and ammonia levels. Kits like our PondCare® Master Test Kit let you measure nitrites and ammonia and pH all in one package. Regularly testing the water quality of your pond will give you the ability to locate potential problems and adjust accordingly before they become a danger to your plants or fish. Your ammonia and nitrite levels should ideally be at 0 with a pH level between 6.5 and 8.5.

Are You Unbalanced!?
So you know why it is important to achieve balance in your pond, you know how to test for it, but how do you go about achieving balance? A great, natural way to combat high nitrate levels in your pond is by incorporating some aquatic plants. Plants like Water Hyacinth filter the contents of the water, helping to create a clean, clear pond. Furthermore, providing adequate filtration is key in maintaining a balanced water body. Pay attention to your fish load. The more fish available to produce waste, the more filtration will be needed to break down the resulting ammonia. A good rule of thumb is to figure one fish per ten square feet of water surface. Adding beneficial bacteria such as Nature’s Defense® will further help to break down organic debris and fish waste. Using natural products and methods like those listed above will reduce your dependency on algaecides and other chemicals to fight algae blooms.

POND TALK: What products do you use to control your water gardens nitrate levels?

PondCare® Master Test Kit - Complete System

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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