Fish need a habitat that provides optimum conditions for growth and reproduction. They need an environment that provides adequate dissolved oxygen, food and shelter. Understanding recreational pond management, water quality, fish introduction techniques and pond aeration can enhance the productivity and beauty of your pond.
Everyone likes to know they have a pond full of fish that are just waiting to be caught. The reality is that most ponds are not fished enough and as fish reproduce, the pond becomes overstocked resulting in reduced water quality for the fish. If you are planning on stocking your pond, we typically recommend stocking bluegill and catfish in the Fall and bass in the Spring. This strategy allows for the bluegill and catfish to grow to sizes to large for the bass to eat. Mid-summer stocking should be avoided since high temperatures result in lower dissolved oxygen concentrations and could lead to increase mortality rates compared to other times of the year.
The most common cause of fish mortality is reduced concentrations of dissolved oxygen (DO). Since fish do not breath air, they push water across their gills and absorb dissolved oxygen in order to breath. The amount of DO fish need to survive increases when they are excited, when they are handled, during feeding time and when water temperatures increase. Unfortunately, when temperatures increase, DO concentrations in the pond are typically low. When DO concentrations reach a critical low point, fish mortality occurs and pond aeration is needed.
Do you need an aerator?
Many pond owners may never ask themselves this question; or they may assume the answer is no… maybe not… or maybe they just don’t know. They’ve owned a pond for a long time and never seen signs that fish needed additional DO . There are three ways that dissolved oxygen is added to a pond: direct diffusion from the atmosphere, wind and waves and photosynthesis, of which photosynthesis is the most important (For more information – A Beginner’s Guide to Water Management – Oxygen and Temperature) By using an aerator, the splashing causes waves resulting in DO being added to the pond (see photo at he top of this blog).
The dissolved oxygen level in a pond changes constantly and this is referred to as the diurnal oxygen cycle. This cycle results in DO concentrations decreasing as the sun sets and continuing to get lower until sunrise when it starts to increase again. Therefore the lowest concentration of dissolved oxygen would occur during the earliest hours of the morning and the highest in the late afternoon.
If dissolved oxygen concentrations are adequate you may not need an aerator; however, if it drops to critical levels having an emergency plan to add DO to the water could help prevent problems from occurring.
Types of aerators
There are many different types of aerators available to pond owners. Some are activated by the PTO of a tractor while others are electric and run during specific times of the day. Common types of aerators include: paddlewheel aerators, pump-sprayer aerators, vertical pump aerators and diffusers or bubblers. Each of these aerators would be used for specific reasons such as cost, labor and efficiency.
Owning a pond can be fun, easy and result in hours of enjoyment if managed correctly. If you are interested in learning more about proper pond management, contact the St. Johns County Extension Office at 904-209-0430 or by emailing me at firstname.lastname@example.org.