Low Dissolved Oxygen: Koi Summer

Protect Your Pond Fish From Summer Heat

The warmest months of the year are times you expect to enjoy your pond and water garden the most, but anxiety arrives if your fish are suffering as a result of a poorly designed & equipped, dirty, overstocked pond that all contribute to low dissolved oxygen. There you are trying to enjoy some time pondside as that Summer warmth cooks the O2 out when the fish need it most. Supplemental aeration helps during these times of Summer by raising the dissolved oxygen levels. “Fish require a certain amount of oxygen in the water – at least 5 parts per million,” according to the University of Florida. “Any lower than that, and they begin to have trouble; when dissolved oxygen levels fall below 2 ppm, an immediate fish kill will occur.”

As Certified Aquascape Contractors, Earth Works of Jacksonville designs and builds healthy, low-maintenance ecosystem ponds and provides annual clean-out services to reduce the potential negative impacts of sludge and debris buildup and their consequential aerobic bacterial breakdown. Ecosystem imbalances can occur along with low DO when pond cleaning is not done as needed, in instances of excessive fish stocking, and where there is excessive algae growth. In addition, sludge and debris buildup is broken down by oxygen-dependent bacteria that further reduces the limited O2 supply available to fish. Small amounts of algae are a normal part of a healthy pond ecosystem. However, excessive nutrient buildup from debris and fish waste can result in algae blooms in your pond, with consequences similar to what’s observed in nature. “Trace minerals or nutrients needed by the algae are occasionally used up, causing some or even all, of the bloom to die back temporarily,” according to Freshwater Aquaculture, at US Department of Agriculture. “The resulting bacterial decomposition and loss of normal oxygen production can lead to oxygen depletions and fish kills.” Fish kills aren’t uncommon with ponders who forget and leave the hose filling the pond and many whose koi outgrew the pond and filtration system without getting it updated in time.

Low dissolved oxygen koi


You want the best for your fish and you know when your wet pets are happy or not. “A habitually low oxygen level can be linked to slow fish growth and persistent fish sickness, and it may contribute to repetitive parasite outbreaks,” wrote Ellen Kloubec for Pond Trade magazine. “Continued exposure to low DO is also considered a precursor to bacterial infections in fish. Even short periods of oxygen deprivation can have damaging effects.”

It can seem like a cruel joke that your koi and goldfish are least active in Winter when they have the most available dissolved oxygen and are the most active when there is the least amount of DO available. So what are some of the solutions if you are experiencing problems with your pond system or want to be proactive in addressing potential threats before they arise? “Turning over the water is the best way to increase oxygen in your pond,” according to Practical Fishkeeping. “Waterfalls are another excellent way of bringing needed movement and gas exchange. As the thin film of water runs down the slope, it absorbs oxygen which then transfers to the pond below. An air pump will also aerate a pond, although many people believe that the bubbles themselves provide the oxygen content. This is not the case, as the increased surface area and water movement do the work.”

To supplement your pond and water garden dissolved oxygen fish requirements Earth Works Garden Center has available several models of Aquascape Pond Aeration kits that increase water circulation and oxygen levels. Unlike small aquarium-style air stones, these aerators provide greater output with large diffuser discs. “Oxygen is transferred as the bubbles rise through the water column,” according to Craig Tucker, Mississippi State University, published by the Southern Regional Agricultural Center and the Texas Aquaculture Extension Service. “Diffusers for large-scale aeration are usually discs, plates, or tubes constructed of glass-bonded silica, ceramic, porous plastic, or flexible perforated membranes. Diffusers are customarily arranged in a grid pattern over the bottom of the pond, with the number of individual diffusers determined by the oxygen transfer rate of the diffuser and the oxygen consumption rate in the water. Oxygen transfer increases with smaller bubble size, deeper bubble release point, and higher oxygen content in the bubbles.”

Although you cannot count on your fish telling you when they are suffering from low dissolved oxygen signs can include lethargy and them hanging out at the surface doing what’s called “piping” the fish version of gasping for breath. Keep your wet pets properly oxygenated for their health and your sanity when you see them suffering.

Low dissolved oxygen koi

If you want a bigger pond for your growing wet pets or you need to get on our schedule for seasonal pond cleanouts contact the Earth Works Landscape Department at 904-996-0712 or email us today! Earth Works designers and staff at the garden center are ready to assist you and we encourage strolls of the garden center ponds, water features and wet pets!

Plus, remember that for comprehensive solutions to your specific lawn, garden and landscaping need contact Earth Works of Jacksonville online and at 904-996-0712.
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