When we look at our ponds, most of us might simply see a body of water with fish swimming in it. But what’s comprised in that water is much more than just that. Many entities factor into what makes our water a dynamic medium for our beloved fish to live their lives. Each one of these entities is dependent on one the other more than most know. Let’s take a look at each entity individually to better understand its needs.
While there are many forms of bacteria present in our ponds, the nitrifying bacteria are the bacteria (Nitrosomona & Nitrobacter, to be exact) that we encourage to grow in our biological filter, or bio filter. These “beneficial” bacteria are responsible for converting the ammonia into nitrite and then later into nitrate, which can be consumed by plants and algae.
The population of these bacteria will increase as the ammonia levels increase, given there is sufficient surface area and oxygen present for their survival. Likewise, as pond water temperatures decrease to 50⁰F or food supplies decrease, these bacteria will become dormant.
If you were to test the pH of your water throughout the day, you would most likely note differences. For example, morning pH levels are most generally lower compared to late afternoon pH levels. The pH swings will depend on the buffering capacity, or the ability to resist changes in pH, of the water. There are buffering products available to help with these large pH swings, if you have a problem.
All living things in the pond are affected by pH. Large fluctuations in pH or highly acidic conditions can stress or kill your fish. In addition, nitrifying bacteria prefer alkaline environment in order to complete the nitrification process. The higher the pH level, the more toxic ammonia becomes. As you can see, a healthy and stable pH plays a key role in the overall health of your pond.
It should stand to reason that the pond temperature will usually be the lowest in the morning and highest at sunset. Pond temperature is affected by the amount and intensity of sunlight, prevailing winds, heat loss due to lack of plants covering the surface, etc.
A good rule of thumb is that the temperature shouldn’t fluctuate over 9⁰F in a 24 hour period. Keep that in mind if moving koi between different temperature environments. An upward temperature movement is tolerated more than a downward movement in temperature.
Oxygen, in the form of dissolved oxygen, is probably the single most important aspect of our pond and yet is so easily looked over. All living creatures in the pond rely on it, including: the fish, the nitrifying bacteria, the plants and even organic decomposition. Oxygen is introduced into the pond when the water comes into contact with the atmosphere, as well as, through pumps, aerators, waterfalls, etc.
Oxygen levels can fluctuate drastically during the day and night, as well as, in hot and cool temperatures. For example, your pond’s oxygen levels can be much lower at night due to the plants actually consuming oxygen instead of producing it, like it does during the day. Another fluctuation example is that warmer water doesn’t hold dissolved oxygen as readily as cooler temperature water. A shortage of oxygen can be noticed by observing the Koi in the early morning when levels would be lowest. Koi are hovering at the surface of the water, gasping for air or if they appear to be lethargic are both signs Koi are suffering from oxygen deficiency. For more on oxygen deficiency and helping control it, read this informative article.
Ammonia levels are an ever-changing entity in the pond world. A few hours after feeding, ammonia levels will be higher due to the fish excrement versus the opposite reading you would get prior to feeding. Interesting enough, it can also be noted that oxygen levels after feeding are lower due the fish metabolizing their food.
Ammonia is found in two forms in the pond: (NH3) and (NH4). It’s fair to say that both of these form of ammonia are present in the pond at all times, one is just more prevalent than the other based on the current pH of the water. Ammonia (NH3) changes to ammonium (NH4) as the pH level drops, and becomes less toxic. As the pH rises naturally during the day, the ammonium converts back to toxic ammonia. So, the toxicity of the ammonia is pH dependent.
It’s good to remember that while Koi have evolved into fairly resilient creatures, helping them to prevent stresses that could weaken their immune system and leave them vulnerable for diseases are what we all strive for. Understanding these individual entities and how they interact with one another can help us to keep our fish and pond a healthy one!