The Danger of Too Much CO2 in Ponds

In an eco system, it is natural for carbon dioxide (CO2) and oxygen (O2) to work hand. Weather the eco system is on land or in water, these two gases co-exist. As the amount of one gas increases, the other decreases.

At dawn, the oxygen levels in the fish pond or water garden are at their lowest. This is because of the processes happening in the pond over night. As the sun rises, the oxygen starts to regain its levels. As soon as the sun sets, the carbon dioxide levels in the pond begin to increase until sunrise the next day. This is a continuous process which makes the pond more prone to algae bloom at night.

Having a UVC (Ultra violet clarifier) or a UV sterilizer will help prevent CO2 from ultimately overtaking your pond and causing suspended algae to grow more. If there is too much algae in the pond, do not expect for the fish in there to survive for another year or less.

Having the right pond aerator will also help maintain the balance of oxygen and carbon dioxide in the pond. What the aerator will do is make the oxygen easily circulate in the whole water system making it evenly distributed so that no living creature will fall short of it. That way, when CO2 levels increase at night, it won’t over power oxygen that much.

Carbon dioxide, just like algae is a natural part of a certain pond. However, if its amount excessively increases then that’s the time it becomes fatal. This gas goes into the pond through the process of photosynthesis in plants and algae and through respiration in creatures like fish and invertebrates. Also Co2 can come from decomposing organic matter on the pond bed such as leaves, tree branches, uneaten food, fish wastes and decaying algae. O2 and CO2 are as equally important as each other. However, if too CO2 accumulates more than O2, the lives in the pond will be at stake since O2 is what they breathe in. And if there is more CO2 than O2, there is an undeniable chance for algae to form blooms. Algae are plant-like creatures that survive through photosynthesis. They consume CO2 which is why it is more dangerous for a pond at night.

If one day you find yourself staring at your pond with majority of the fish floating dead, there are things that are most likely to have occurred during the time you weren’t able to check on the water system. One is that some predatory animals like cats or birds have attacked and killed the fish. The other is the presence of too much algae which you obviously didn’t notice flourishing. For algae bloom to happen, it requires excessive abundance of CO2 and extremely low levels of O2.

Keep in mind that the amount of CO2 is higher in warm seasons and O2 on the other hand is higher in cold seasons. But still, CO2 has a bigger chance of overtaking the pond because O2 can only be produced in the presence of sunlight.