Healthy Ponds Have Healthy Bacteria - How to Keep Your Biological Filtration in Shape

Healthy Ponds Have Healthy Bacteria
How to Keep Your Biological Filtration in Good Shape

Was it unseasonably cool and wet this spring? — Or was it normal and we’ve had so many hot, dry, drought-ridden springs that we no longer know what normal is? I don’t know the answer but I do know that the cool, rainy weather we’ve experienced throughout this whole spring has caused a lot of concern for the development of nitrifying bacteria and resulting water quality problems.

Nitrifying bacteria, the bacteria needed to convert waste to fertilizer in ponds, need warm water temperatures in order to colonize. In winter nitrifying bacteria die back and do not grow back until the pond warms up in spring. Usually this bacteria is up and growing strong by mid-April or May. It’s already June and some of us are still having water quality problems that we can attribute to not having enough active bacteria in our systems to support our fish load.

The first of the two important nitrifying bacteria to develop in spring is nitrosomonas. This friendly fellow converts ammonia (waste that fish and dying plant material give off) to nitrites (with an “i”). Nitrites are still deadly and we need the second friendly bacterium, nitrobacter, to change nitrites to nitrates (with an “a”). Nitrates is basically fertilizer and your plants will love you for it! Nitrobacter is the last to grow and requires warmer water than nitrosomonas in order to develop.

Ammonia burns the gills of the fish and makes it difficult for them to breathe. If caught in time it’s possible that a fish, though weakened, can heal and survive once the ammonia is taken away. Nitrites cause the blood of the fish to turn brown, thus starving the fish of oxygen-enriched blood. Fish literally suffocate from lack of oxygen and it becomes a slow death for them. Salt will inhibit the intake of nitrites into the blood but only at lower levels. Though performing a salt treatment will help, it is not a fool-proof method of preventing nitrite poisoning and should only be used in conjunction with other efforts to increase the growth of nitrobacter and totally rid the water of nitrites.

Testing for Ammonia and Nitrites

If your fish are dying or acting strangely and you call us for help we will ask one very important question. Have you tested the water for ammonia and nitrites? We aren’t asking you this just hear ourselves talk. Poor water quality is the #1 fish killer! The tests are easy to do and inexpensive and they are a staple in any pond person’s supply chest.

Healthy, carefree water quality is when you have NO traces of ammonia or nitrites when you test your water. Another important water factor is a stable pH — but that’s another article. When the water tests negative for any trace of ammonia and nitrites it means both nitrosomonas and nitrobacter are happy, happy and your biological filtration is in great shape.

We can tell a lot more about the development of your nitrifying bacteria than most people realize from the results of the water tests.

Let’s look at several possible test result scenarios:

#1 Scenario

Tests show 0 Ammonia and 0 Nitrites

Your water’s great. Go home, have a beer and enjoy your pond!

#2 Scenario

High Ammonia, 0 Nitrites

Before you start celebrating that you have no nitrites let me tell you that this scenario is the absolutely worse we want to see! This means that nitrosomonas is not there at all to change even a small amount of ammonia to nitrites so of course you won’t have nitrites — yet.

#3 Scenario

High Ammonia, Low Nitrites

Okay. That’s one step better. It means nitrosomonas is being a bit lazy because you do have some nitrites that have been converted from ammonia. Nitrobacter, however, hasn’t even gotten out of bed.

#4 Scenario

0 Ammonia, Any Reading of Nitrites

You are officially half the way to nitrifying heaven! Nitrosomonas has gone to work but nitrobacter is still lazy.

What Causes Slow Growth of Nitrifying Bacteria

Nitrifying bacteria require warm water temperatures and well-oxygenated waters to flourish. The reason why we’ve had so many problems this year with ammonia and nitrite readings is that every time we thought the weather was getting warm a blast of cold rain came in to cool it back off. Fish were already eating and spawning which added more proteins and waste to the pond and even the most seasoned filters had trouble keeping enough nitrifying bacteria alive and healthy because of how cool the water stayed.

Seasoned filters and ponds become healthy with active nitrifying bacteria much quicker in the season than a new pond or a sterile filter. New ponds and new filters must develop these bacteria in order to become healthy life-giving homes to fish. This spring the new pond and new biological filter had a more difficult time than normal with building up its nitrifying bacteria.

There are many factors other than a cold spring and a new pond that affect the growth of nitrifying bacteria.

An ultraviolet water clarifier (UV) kills some degree of bacteria, good and bad, while it sterilizes water-borne algae. If sized correctly, however, once nitrifying bacteria is healthy in the biological filter, the UV will not kill enough bacteria to hurt. It’s during the time that the bacteria is weak and growing that we should refrain from using the UV.

Cleaning the filter with chlorinated water can kill young, growing bacteria. Bead filters use de-chlorinated pond water to clean the filter but other filters rely on water from the garden hose. Once again, while it might not hurt to spray filtering material with chlorinated water from the garden hose when the bacteria are strong, it is best to refrain from zapping weak bacteria with chlorinated water during the time when bacteria needs all the help it can get.

On the same hand, performing a thorough filter cleaning or bead filter maintenance too late in the season has the potential to destroy all your biological filtration. It’s best to hold off until late fall or very early spring before performing a yearly, thorough filter maintenance.

Don’t scrub the sides of your pond, ever, unless you want to destroy the “seasoning” of the pond and much of its nitrifying bacteria and healthful immunity-building conditioning. The gel that builds up on the sides of the pond is good stuff. Keep it!

Water treatments designed to help combat bacterial infections cannot distinguish between good (nitrifying) and bad (anaerobic) bacteria. The water must not flow through the biological filter when using any of these medications. The only exception that comes to mind is Melafix - and that’s because Melafix is more of a tonic and does not work by actually killing bacteria. Do not simply turn off the pump when using a bacterial product because you may end up with dead fish from lack of dissolved oxygen. Instead, reroute your water so that it by-passes the filter. A good bead filter allows the option of running on a by-pass setting so the medicated water goes through the valve without ever touching the filtering media. Other types of filter systems can be plumbed with valves to by-pass the filter material when desired. Another option is to run a separate pump with a hose re-circulating the water without it flowing through the filter.

Another (sometimes unavoidable) nitrifying nightmare is when the pond experiences a pH crash. This is when the pH suddenly plummets down to 6.0 or less. It usually happens in the wee hours of the morning when the pH is naturally at its lowest. A pH crash has the potential to kill all the nitrifying bacteria in the filter, thus, the filter crashes as well! Avoiding a pH crash is the key. Keeping a stable pH is a must. It’s a good idea to periodically check the pond water for pH alkalinity (aka pH stability). Add pH Stabilizer if the pH is not stable.

Overcrowding a pond can spell disaster. It may rock along well for a couple of years then one day — when one least expects it — whammo! The largest fish dies followed by another, then another. Water tests will reveal ammonia and nitrite build-up where it never was before. This is a waiting time bomb. Sometimes the pond can be so overcrowded that no amount of filtration will cure the problem. The only cure is to thin the pond and keep it thinned. A rule of thumb for the amount of fish a pond with good biological filtration can hold safely is 1 koi per 100 gallons or 1 goldfish per 50 gallons. — But who’s to say what “good filtration” is! That, too, is another story.

Seeding the Biological Filter

If the pond or filter is new or if the biological filtering system has crashed one must basically start from scratch to seed his filter. Below are listed ways to kick start the growth of nitrifying bacteria.

Make Sure the Biological Filter is Big Enough — One can never have too much filtration. The heavier the fish load the more filtration is needed. If the filter is not adequate it will need constant cleaning and will not do a good job of housing enough bacteria.

Add Enzymes — Some enzyme products are better at helping build up the bacteria than others. MicrobeLift PL is our favorite for encouraging the growth of nitrifying bacteria while MicrobeLift's Super Start Bead Filter Bacteria is wonderful for systems with bead filters.

Hold Off Cleaning the Filter — As long as the filter is not clogging up the water flow and until the nitrifying cycle is established do not clean the filter. If it must be cleaned use de-chlorinated water from the pond.

Turn Off the UV — While the filter is seeding unplug the UV. Green water may be ugly to some of us but it’s not necessarily unhealthy. It’s better to allow the nitrifying bacteria to establish well before turning on the sterilizer.

Do Not Feed the Fish — Don’t worry. The fish may get mad but they don’t understand that it’s for their own good. The more food the fish eat the more waste in the system to convert to fertilizer. Resume feeding when the tests for ammonia and nitrites come back negative for a week.

Use Ultimate — This new product renders the affects of ammonia and nitrites harmless to the fish up to a certain level. Always use a PondCare drop test kit whenever you use Ultimate so your readings will be correct.

Perform Water Changes — Test the water every day. Change the water (remember to de-chlorinate tap water) if the ammonia is over 1.2 ppm and/or the nitrite reading is over 2 ppm if using Ultimate. If not, change the water whenever there is any reading of ammonia or nitrite. Keep monitoring and making water changes as needed until the filter is seeded.

Thin Out an Overcrowded Pond — It’s hard to make the decision of who stays and who goes but it’s for the good of all the fish. Give the extras away or build another pond for them (like we have done a couple of times!).

Keeping Nitrifying Bacteria Healthy and Plentiful

Once the biological filter has seeded there are a few things one can do to insure that the nitrifying bacteria stay healthy.

Maintain Stable pH — Add pH Stabilizer to the pond if the alkalinity is not stable. This product should hold the pH in place for many months or until the water has been changed. Test for pH and Alkalinity periodically.

Use Enzymes — Use maintenance doses of products that promote healthy enzymes and bacteria. A good product to use for this purpose is MicrobLift or Super Start Bead Filter Bacteria.

Do Not Overfeed the Fish — One can tell how much (and how many times) the fish can be fed by how good the water quality stays. If one experiences ammonia and nitrite readings occasionally this indicates the filter is not strong enough for the amount of waste it must process. Adjusting the amount of food allowed to the fish and increasing the amount of biological media can often correct this problem.

Once a biological filter is seeded the pond becomes easy to manage. The only way to get to that point is to grow and maintain healthy nitrifying bacteria. Next spring we may not experience the same unusually cool weather but if we do it is best to keep these simple yet necessary steps in mind. The loss of its nitrifying bacteria is one of the most aggravating things that can happen to a pond. Knowing how to detect ammonia and nitrite problems through testing and how to encourage new nitrifying bacterial growth will prevent it from becoming a fish health disaster as well.

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