| Algae Bloom Causes Carbon Dioxide Levels To | | | | deaths are significantly reduced. |
| Rise At Night | | | | It is also much easier for atmospheric oxygen to |
| Carbon Dioxide (CO2) And Oxygen (O2) work | | | | dissolve in cold water than it is for it to dissolve in |
| hand in hand in a garden pond. As oxygen levels in | | | | warmer water. In addition cold water is able to |
| the pond water increase, the level of carbon | | | | hold more oxygen than warm water. Have you |
| dioxide decreases and vice versa. This is a natural | | | | ever noticed pond fish gulping for air at the pond |
| process. Oxygen levels are at their lowest at | | | | surface on hot, sunny days? This is the reason |
| dawn, due to the processes taking place in your | | | | why. |
| pond over night. During the day as sunlight | | | | How Carbon Dioxide Affects Pond pH Levels |
| appears the level of oxygen rises, peaking when | | | | The ideal pH for garden pond water is between a |
| the sun sets. After sunset the carbon dioxide | | | | pH of 7.5 to a pH of 9. Carbon Dioxide dissolves in |
| which is at its lowest at this time of day starts to | | | | water to produce carbonic acid (H2CO3), which |
| rise, peaking just before sunrise. It is important to | | | | has a pH of less than 7. As a result the pond pH |
| not let carbon dioxide spikes, caused by green | | | | will drop and become more acidic as the carbon |
| algae blooms from killing your pond fish. The best | | | | dioxide levels increase in line with the increased |
| way to do this is to use a UV clarifier or a UV | | | | respiration from aquatic life. This is exactly what |
| sterilizer. | | | | happens during the night in your pond. During the |
| How Does Carbon Dioxide Get Into My Pond? | | | | day the opposite is true, where photosynthesis |
| Carbon dioxide is produced by aquatic pond life | | | | boosts the increase in oxygen, causing the pH |
| such as fish, snails, algae and aquatic plants | | | | level to rise and become more alkaline. It is when |
| through respiration (breathing). It is also produced | | | | the pH level drops and becomes more acidic that |
| as a result of rotting organic matter on the pond | | | | the potential for carbon dioxide problems increase. |
| floor, including leaves, uneaten fish food and | | | | What is Pond pH? |
| decaying algae blooms. | | | | The pH scale which ranges from 0 through to 14 |
| Carbon Dioxide Spikes Cause Fish Fatalities | | | | signifies whether or not the pond water is acidic |
| Here is a question for those of you who have a | | | | (below pH7) or alkaline (above ph7). A pH of 7 is |
| fish pond! Have you ever woke up in the morning | | | | neutral. The higher the number of free hydrogen |
| and found several of your pond fish dead? You | | | | ions (H+), the more acidic the water is. A neutral |
| probably stood there scratching your head, | | | | pH means that the number of positive hydrogen |
| wondering why? There are two likely causes: | | | | ions (H+) are the same as the number of |
| * A predatory animal such as a bird or a cat has | | | | hydroxyl ions (OH-). |
| physically killed the fish. The tell tale signs should | | | | Aeration Increases Oxygen Levels and Reduces |
| be fairly obvious; damage to the body or head, | | | | Carbon Dioxide |
| for example. | | | | Garden ponds can never have too much oxygen. |
| * If your pond suffers from heavy algae blooms | | | | A well aerated garden pond will suffer |
| then the most likely cause is suffocation, through | | | | considerably less from the catastrophic effects of |
| lack of oxygen. The pond water will need to have | | | | high carbon dioxide levels, such as fish fatalities. |
| contained high levels of carbon dioxide and | | | | Using a waterfall, water feature or pond air pump |
| extremely low levels of oxygen for this to have | | | | will add valuable oxygen to the pond environment, |
| happened. | | | | which will push the pond pH up and remove |
| If the cause of the deaths is due to the high level | | | | carbon dioxide from the pond water. |
| of green algae blooms then the best way to | | | | Pond Buffers Increase Pond pH Levels |
| remedy this situation quickly is to install a UV | | | | A buffer is any substance that reacts with an |
| clarifier or UV sterilizer, as these units will usually | | | | excess of hydrogen ions (H+). The most |
| manage to get the algae bloom under control | | | | commonly used buffer is Calcium Carbonate |
| within about 5 days. With continuous use a UVC | | | | (CaCO3) which is frequently used in garden ponds |
| light will keep your pond water free from algae | | | | to prevent the pH from becoming acidic. It is a |
| bloom. Please note however that a UV will not | | | | good idea to add a buffer to your pond filter to |
| remove blanket weed or other filamentous string | | | | prevent fluctuations in pH levels. |
| algae types. | | | | CO2 + H2O ---> H2CO3 ---> H+ + HCO3- |
| What Is Photosynthesis? | | | | In the above example, carbon dioxide + water |
| Planktonic algae are a form of microscopic plant | | | | form carbonic acid. This disassociates into two |
| life that consumes carbon dioxide, during the day | | | | ions; including a free hydrogen (H+) ion. |
| and reverts to using oxygen at night time. All | | | | CaCO3 + H+ + HCO3- ---> Ca (HCO3)2 |
| plants carry out a process known as | | | | In the above example, a buffer such as calcium |
| photosynthesis. Photosynthesis uses the energy | | | | carbonate (CaCO3) bonds with the free hydrogen |
| of the sun to convert inorganic carbon (gained | | | | ion, to form Calcium Bicarbonate Ca (HCO3)2. |
| from CO2 dissolved in the water) into carbonic | | | | As long as you have calcium carbonate in your |
| acid (H2CO3). During sunlight hours plants and | | | | pond filter, your pond water will be protected |
| algae absorb carbon dioxide from the pond water, | | | | against swings in pH. A buffer will also work in |
| causing the level of carbonic acid to fall. This | | | | reverse; releasing hydrogen ions back into the |
| causes the pond water to become more alkaline | | | | water should the water become excessively |
| i.e. the pH level increases. | | | | alkaline. |
| Carbon Dioxide Problems Are Lower In Winter | | | | A pond should be a real enjoyment and will be if |
| Oxygen levels in pond water are at their highest | | | | you are aware of what is actually happening |
| during the colder fall and winter months when | | | | below the surface. My advice to you would be to |
| there is significantly less biological activity taking | | | | ensure that you use a branded biological pond |
| place within your garden pond. There is an overall | | | | filter, a reliable energy efficient pond pump and a |
| reduction in the level of nutrients (nitrates and | | | | UVC sterilizer or UVC clarifier. Ideally you should |
| phosphorous) present in the water. This is mainly | | | | add additional oxygen into the pond water; water |
| due to the plant life and pond life producing less | | | | falls and pond air pumps are the best way to do |
| waste; the plants have stopped growing and pond | | | | this. |
| fish feed less. There is also less sunlight resulting in | | | | Remember to ensure that you regularly check |
| algae populations diminishing. For this reason the | | | | your pond water for ammonia, nitrite, pH, total |
| overall fluctuations between oxygen and carbon | | | | Alkalinity and possibly hardness using a suitable |
| dioxide levels during the day and at night will be | | | | pond test kit to quickly identify any potential |
| significantly less. The chances of Koi and goldfish | | | | problems. |