Mother Nature's Balancing Act - The Nitrifying Cycle

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Sometimes it “just happens”. Sometimes it seems it never will. A balanced pond is what we all desire because it provides a safer environment for aquatic life and a cleaner pond for us to enjoy.


Mother Nature has a way of balancing her own water systems. She continually runs fresh water through her lakes and streams and adds just enough life to the waters to keep them healthy and void of toxic substances. She doesn’t overpopulate her waters. Though it may seem cruel she allows only the strongest individuals of each species to survive so that the species itself remains healthy. She keeps her water balanced by creating what we call the Nitrifying Cycle.


The Nitrifying Cycle


Fish naturally eat worms and algae and other organic materials that might be present in the pond. Just like humans fish create waste. Also just like with humans waste is toxic to the fish. Fish waste and dead leaves create ammonia in the water and if the nitrifying cycle is not functioning the ammonia in the water will kill the fish. Mother Nature’s way of solving this problem is to create a bacteria called Nitrosomonas that converts ammonia to nitrites. Nitrites is still very lethal to fish so Mother Nature creates another bacteria called Nitrobacter that converts deadly nitrites to nitrates which is basically fertilizer. Plants in the water, including algae, take nourishment from these nitrates and reduce the amount of nitrates in the water, rendering the water fish safe. Of course, then the fish eat the plants and the cycle starts all over again.


When either of the two beneficial bacteria, Nitrosomonas and Nitrobacter, are not present in the pond the water will test high in ammonia and/or nitrites.


Complications of Ammonia


The presence of high ammonia will burn the gills of the fish and the fish will die unless the ammonia is neutralized by an ammonia blocker or an immediate water change is made. The fish can’t breath if their gills are damaged and you’ll notice that they hang by the water return or float at the top of the water as if gasping for air. Upon examination, the gills are gray in color or the tissue appears burned away. There is good news if the fish survive the initial ammonia spike. The tissue does regenerate over time and the fish should return to good health.


Nitrite Poisoning


The term “Nitrite Poisoning” is used whenever fish experience complications from a high content of nitrites in their water. It doesn’t act like ammonia and burn the gills. Instead, nitrites travel through the blood system, poisoning the fish and turning the blood brown instead of red. Nitrites can be more deadly than ammonia simply because it stays with the fish longer and can do more permanent harm. An immediate water change is once again necessary if the water tests high in nitrites. Adding non-iodized salt to the water will help neutralize the continuing intake of nitrites into the fish’s blood system. Other corrective action must be taken along with the salt. Since high nitrites indicates a low presence of the Nitrobacter bacteria (the one that changes nitrites to nitrates) it is necessary to help establish the bacteria by cutting down on feeding, reducing the fish load and/or increasing biofiltration.


High Nitrates


Nitrates are basically fertilizer for plants. Until recently nitrates were not taken seriously and testing for nitrates was not encouraged. Studies have shown that high concentrations of nitrates can be harmful to fish. High nitrate readings in water have been attributed to swim bladder problems, such as fancy goldfish turning upside down. In fact, in all our tanks that house fancy goldfish that are beginning to “flip over” we found high readings of nitrates. Though we’re not convinced yet that high nitrates is the culprit we’re taking testing for nitrates more seriously and considering high nitrates a stress factor. High nitrates are associated with blood in the fins and weak fish. An easy way to bring down the concentration of nitrates is to add plants to the tank to consume the fertilizer.


What Throws Us Out of Balance


Mother Nature continually refreshes her water by way of streams and rivers. A stagnant lake becomes a death trap for aquatic life. If a tally was done, we’d probably find that her ratio is one fish to a couple of thousand gallons of water! I’ve seen our decorative ponds where the ratio is more like ten fish to one-hundred gallons of water. That’s why ponds constructed by man (or woman...) cannot rely on “natural filtration” methods such as using plants as the only filtration. That’s why we preach the importance of adding biofiltration. We are the ones who throw Mother Nature’s balance off by exceeding the fish-to-water ratio and by recirculating the same water. We create our own little water world and place aquatic life into it. It’s our responsibility to attain and maintain balance in the pond.


How Do I Balance?


Let me count the ways...ONE!


Install biological filtration. True biofilters, such as the ProBead, not only take solids out of the water to help keep your pond clean, they provide housing for those two very necessary nitrifying bacteria, Nitrobacter and Nitrosomonas.

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The one question that is asked of me most often is How do I get rid of this green algae? Algae tends to show its ugly face in early spring when the water temperature starts rising. Left over leaves, mulm, fish poop, etc. from Winter triggers Mother Nature to start her nitrifying cycle of converting ammonia to nitrites and finally to nitrates.
Certain biological processes must occur before a pond is fully seeded and balanced. Nitrifying bacteria must be present and working in the pond’s ecosystem before the pond can promote a healthy environment for aquatic life. New ponds will have none of those necessary biological processes in place. This creates a “New Pond Syndrome” that can be frustrating if the new pond owner is not equipped with knowledge on how to deal with it. Giving the pond time to develop these processes is the most important step and there are things that we can do to hasten the development.
Definite noticeable changes occur in koi and goldfish, plants and the pond itself as the temperature of the water begins to drop. Leaves on water plants start to brown and die back. Koi and goldfish become less active and require less food. Leaves fall and cover the surface of the pond. The pond may suddenly clear up after not being clear all year. These are changes we see. The changes we do not see are just as important. Nitrifying bacteria, present all spring and summer in the biofilter, stop reproducing and become none effective. Biological functions in the fish’s bodies, controlled by temperature of the water, slow down and eventually the fish hover at the bottom of the pond in a state of semi-hibernation.
Now that spring is just around the corner it’s time to begin the loving task of opening up the pond. The transition of winter to spring can be tricky for the fish. Parasites and anaerobic (bad) bacteria thrive in cool waters before the fish have had time to build up their immunity. Aerobic (good nitrifying) bacteria take their time to establish in the biological filter so we run the risk of deadly ammonia and nitrite build-up in the pond during this time of year.
Early spring is the perfect time to clean and perform maintenance on your biological filter. During winter the water is too cold for nitrifying bacteria to live and they go dormant. As water temperatures heat up nitrobacter and nitrosomonas, the two “good” bacteria begin to colonize. If you clean your filters with chlorinated water the chlorine can prohibit the growth of these two beneficial bacteria — especially nitrobacter which, of the two, is the slowest to grow.
Most folks are going to grab whatever is handiest and cheapest for the fish in their ponds. Little thought is given to what kind of food it is and for what purpose. The fact is ornamental pond fish really DO NEED to be fed because Mother Nature cannot supply worms through rubber liners. We, at Pond Doc’s, DO look at the label and size up just what the food does for the fish. Some brands are extremely poor quality and build fat on the fish. Yes, fish suffer from obesity just like humans do! Others are on the other end of the spectrum, supplying the equivalent of our steaks and caviar.