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Fish:
A pond without fish is just another pretty Water Garden. Decorative fish add the crowning touch to a pond with their constant motion, occasionally flashing in the sunlight, and their myriad color patterns ever changing the visual impact of aquatic scene.
Choosing fish for a pond is no more than a matter of personal taste. Your options include Koi and Butterfly Koi (Domestic and imported) and Goldfish (Comets, Sarassa comets, Shubunkins and Fancy Fantails). Other fish include Oranda, ranchu, lionhead and ryukin. These latter are not wise choices as they will not usually survive the winter. Mosquito fish should not be placed in a pond with valuable fish because they are known to carry disease and parasites without ever appearing sick.
Whichever fish you choose to add to your Pond certain parameters must be observed and maintained. All pertain to water quality. This is where our food chain or cycle from the Pond Biology page really starts and it begins with fish waste. This waste is mainly in the form of nitrogen. If not for the bacterial process to break it down it would accumulate and eventually kill everything in the pond. We can test for all forms of nitrogen. These forms are-
- Ammonia: It is the main nitrogen waste of fish produced as a by-product of respiration. High ammonia levels are indicative of low levels of beneficial bacteria. Other causes may be a undersized or clogged filter, a fish dying and left in the pond to decay or just simply overfeeding your fish. This is converted to nitrites by nitrosomona bacteria.
- Nitrite: This is produced by nitrogen reducing bacterial action on ammonia. Nitrite levels as low as 0.1 ppm are toxic to fish. Nitrites are broken down by another bacteria called nitrobacter. Nitrates are a result of this action.
- Nitrate: This is the final product of the nitrogen cycle. Plants and algae use nitrates, together with other nutrients, for growth. High nitrate levels are not in themselves toxic but indicate poor water quality. Nitrate levels should never exceed 80 ppm in your pond. Increasing the number of aquatic plants will keep levels acceptable.
pH is the next parameter that we will focus on. pH is the measure of the acidity of a solution and is defined as the logarithm of the reciprocal of the activity of free hydrogen ions, which means that a change of one unit in pH equals a ten-fold change in the activity of hydrogen ions. If you do not understand what you just read just remember that pH is very important. The optimum pH range for aquatic life is between 5.5 and 8.0. Koi and goldfish tolerate pH levels exceeding this range, however the majority of plants prefer a pH between 6.5 and 7.5. As the pH level rises so does the toxic effects of ammonia. On the other hand, pH levels can drop rapidly due to low oxygen levels, high carbon dioxide levels, the decay of organic matter and the normal activity of nitrifying bacteria. Carbonates in the form of baking soda, oyster shell or any commercial buffer will stabilize levels as pH is supported by alkalinity, or carbonates.
Oxygen is the last, but equally important, parameter we will cover. Oxygen levels in a pond are critical to the existence of any form of aquatic animal life. Oxygen enters the water in two ways:
- From the natural exchange of gases at the water surface.
- From submerged plants during photosynthesis.
It is important to understand Solubility and DOC (Dissolved Oxygen Content). Solubility is the capacity of oxygen to be dissolved in water. Solubility is a function of temperature and barometric pressure. It decreases as the temperature rises and increases as barometric increases. DOC is controlled by barometric pressure, water temperature and light.
The demand for oxygen by fish rises as the temperature rises. This is due to the fact that fish are cold-blooded. As the temperature rises the metabolic rate of fish increases which results in a higher oxygen demand. This results in potential problem. As oxygen demand by fish rises the Solubility and DOC decreases. This is why, on a hot summer day, it is not unusual to see fish at the waters surface gulping air. The availability of oxygen is low.
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