Alkalinity is your friend.

One of the most misunderstood concepts of pond or container management is alkalinity and the pond’s relationship to acid balance.  Alkalinity and pH are linked in the sense that alkalinity is a measure of the amount of acid that your water can absorb without changing the pH. Dissolved chemicals protect the body of water from rapid environmental pH changes. We are talking about the carbonate cycle as it connects with an acid-base balance of water.  In the oceans, alkalinity is based on the reaction between carbonate/bicarbonate. It is the same with fresh water but the level of carbonate/bicarbonate varies greatly between bodies of water; this often determines the kind of fish contained within, depending upon their ability to thrive in particular water chemistries.  Different mixes of chemicals will provide a buffer system that reflects a certain pH level. As an example: the African Rift Lake Cichlids require pH from 7.6 to 8.6. Discus from the Amazon are looking for pH 6 or below. As pond and aquarium curators, we have many tools at hand to monitor pH and alkalinity. We also have the chemicals to make necessary adjustments. A number of companies that produce exceptional products for this purpose: SeaChem,  Aquarium Pharmaceutical and Ecological laboratories to name three. Keeping track of the levels of alkalinity will help insure that your pH remains stable.

A mistake that many make is the use of pH up and pH down. These are acids and bases. I want to stress that these products do not add alkalinity to insulate the water from fluctuating all over the charts — which is all you’ll inevitably accomplish by alternating pH up and pH down to correct pH imbalance.

How do we adjust our alkalinity and pH?

First we have to monitor pH.  A problem that arises when monitoring pH is that during the day pH can be okay or even a little high in the acceptable range but if you check in the very early morning it may be very low. This is a result of the interaction between low alkalinity and the light/dark reaction of the plants. You can have the proper pH but the alkalinity in your water may be so low that your daily fluctuations take you out of your preferred range. You need to test alkalinity to determine the weak link in your aquatic management.

The best kits require only a couple minutes of your time. I like the Hagen and Red Sea kits — really any of the kits based on the Hach and LaMotte research.  An easier but not necessarily accurate test is to use strips. These strips will most likely work just fine as long as you’ve made sure to keep them dry before use. Even environmental humidity on exposed strips might disrupt your tests.

Where does the acid come from?

A number of places.

1.       Leaching of some acid soils into the pond can add acid.

2.      Rain can be quite acidic because of coal-powered energy plants and industrial pollution.  Power plants and industries that use coal spew a lot of sulfur into the air that becomes sulfuric acid when it combines with water.

3.      The respiration of animals, especially in a highly populated pond, produces acid.

4.       Decomposition of leaves and algae growing in pond.

Your pond pH can radically change with a lot of rain!

The problem that arises from rain is that it dilutes the water and reduces alkalinity.   People think that ponds are natural and don’t need to be tested like aquariums.  This is completely false.  When it rains, the water in your pond is being diluted by water from the rain that is devoid of buffer and therefore usually acidic.  Enough rain might dilute your buffer to the point that your water cannot maintain its own pH. This can lead to a funeral service for your fish.

As a side note: when buffering is limited, the pH will rise during the day. Plants use CO2 which reduces acid through a dynamic system called the carbonate cycle, and the pH can rise rapidly. At night plants use O2. The acid level then goes up because as O2 is used for plant respiration, CO2 goes up. The CO2 reacts with water to produce carbonic acid.  Carbonic Acid is an organic acid that can change your pH if adequate buffering is not available to absorb the change.

Summary:  Use dip strips from Jungle, Mardel, or Rainbow Lifeguard that allow you to get an approximation of the alkalinity and pH of your water.  The five way strip also will give you an idea of the nitrate content of the water. For goldfish and koi the pH should be a little higher than neutral (7.0 pH).  This is not an exact science for the pond owner (it is for an aquatic biologist) but to keep tabs on the ability of your pond to maintain pH is a very good way to prevent fish and plants from dying. Happy fish and healthy plants make for a happy pond owner.

As a suggestion… if the pond owner gets a “trash pump” (they don’t easily clog with debris), he can water his plants and change water at the same time.  Use the pond water to hydrate terrestrial plants and replace the water out of your hose but make sure to use de-chlorinator.  Using this water for your indoor plants is also a very good way to keep house plants. They love the aged water with low levels of nitrogen and phosphorous. Modern city water is a destructive combination of chloramines that fish find particularly harmful.

Above all, respect your water!