Will Hehemann | School of Agriculture, Fisheries and Human Sciences
In between summer fishing sessions, Arkansas farm pond owners can consider taking some steps to increase their pond’s bounty of fish, Scott Jones, small impoundment Extension specialist at the University of Arkansas at Pine Bluff, said. Starting a fertilizer or feeding program can increase the size of fish populations in the pond, as well as the size of the individual fish.
“Ponds with dwindling or stagnant fish populations, or ponds that have always been unproductive, can benefit from fertilization,” Jones said. “Fertilizer introduces more nutrients into the water, which allows for planktonic algae to grow more dense. This thicker bloom of algae then supports a larger crop of herbivorous zooplankton. The plentiful zooplankton support larger populations of forage fish, which in turn support the growth of more sportfish.”
Before starting a fertilization program, pond owners should carefully consider whether their pond actually needs the added nutrients, Jones said. Most Arkansas ponds already receive plenty of nutrients from their watersheds and usually do not need extra nutrients.
Ponds must have relatively stable water chemistry for fertilization to work consistently, he said. The alkalinity of water, or its ability to neutralize acid, can buffer and maintain the pH scale in a range that makes nutrients available for plants to use.
Water alkalinity is a simple parameter to test to ensure proper water chemistry, Jones said. Pond owners can order affordable alkalinity test kits online or contact their local Extension office to test the alkalinity of their pond.
Pond owners should maintain a minimum alkalinity of 20 milligrams per liter of calcium carbonate (CaCO3) in their ponds by applying agricultural limestone. Typical application rates of agricultural limestone are one to two tons per acre, but it can often take more in central and southern Arkansas.
“Generally you shouldn’t fertilize ponds that are muddy or weedy, have existing plankton blooms or have an excessive water flow,” he said. “You should also avoid using fertilizer if you regularly use fish feed or if your fish population is already out of balance.”
At the store, fertilizers are labeled according to their nutrient content and product form. The nutrient content is listed as three numbers that represent the percent of nitrogen (N), phosphorus (P2O5) and potassium (K20) available in the fertilizer. Therefore, a 10-52-0 fertilizer contains 10 percent nitrogen, 52 percent phosphorous and 0 percent potassium.
When shopping for the right fertilizer, pond owners should choose a product high in phosphorous, as phosphorous is the primary limiting nutrient in ponds and the most effective at spurring planktonic algae blooms, Jones said.
Fertilizers are available in liquid, granulated and powdered forms. Liquid fertilizers usually require dilution before being applied, but they are immediately effective because they are already completely dissolved. Powdered fertilizers tend to be more expensive than granulated fertilizer but they also dissolve much more quickly.
“Granulated fertilizers are usually the easiest to find in stores,” Jones said. “When applied in a pond, this type of fertilizer cannot be allowed to settle to the bottom of the pond, as much of the phosphorus in the granules will bind to the mud and be wasted. A solution to this problem is to cut a large X shape across one side of the fertilizer bag and place the bag in shallow water with the X-side facing upward, allowing the granules to dissolve and disperse throughout the water.”
Jones said fertilization should be maintained throughout the growing season and discontinued when water temperatures fall below 60 degrees. Once a fertilization program is started, it should be continued each year because the total weight of fish in the pond will increase and the fish will begin to depend on the additional food available as a result of fertilization.
After initial fertilizer applications have been made, pond owners should monitor how the pond responds to the added nutrients. The water should develop a greenish or green-brown color within a week or so. Pond owners should allow two weeks between applications in order to monitor the results of each addition.
Jones said pond owners should periodically check the density of the algae bloom in order to decide when it is time to fertilize again. A simple and effective tool to measure bloom density is a pie tin nailed to the end of a yardstick.
Lower the pie tin into the water until it just disappears from view and then raise it until it can just be seen again. Measure the depth of the bloom from the water’s surface by examining the mark left by water on the yardstick.
In farm ponds, between 18 and 24 inches of visibility is ideal, he said. If the bloom is thicker than this and the measurement reads less than 18 inches from the water’s surface, the pond should not be fertilized. If the bloom is thinner and the measurement reads more than 24 inches away from the water’s surface, the pond can be fertilized again.
Jones said fertilization is not the only way to increase the production densities and growth of fish in a pond. Pond owners who choose not to fertilize their pond can start a feeding program to increase their fish population. However, those who are already applying fertilizer to their pond should use caution when adding feed to the pond.
“A combination of fertilization and feeding is not commonly recommended in private ponds because with increased nutrient input comes increased risk of oxygen depletion from decomposing organic matter and the threat of excessive planktonic algae blooms,” he said. “Uneaten fish feed essentially becomes fertilizer on top of the fertilizer that was already applied.”
Jones said many species of fish including catfish and bluegill will eat prepared feeds. Predators such as largemouth bass and crappie will not eat these feeds, but will profit indirectly as they eat smaller fish such as bluegills and minnows that eat the feed.
Feed is particularly beneficial in lakes and ponds where the production of natural food is limited by low nutrients or other water quality problems, he said.
Jones recommends using a floating feed and only applying an amount that the fish will eat between five to ten minutes. Feeds labeled for catfish and that contain at least 28 percent protein are a good, inexpensive choice of feed for most ponds. Feeds that contain higher protein levels are more expensive and unlikely to produce more fish.
“Fish can be fed daily, every other day or as little as one or two times a week depending on the owner’s budget and energy level,” he said. “The important thing to remember is that once a feeding program is started, it should not be abruptly stopped because the individual fish and the whole fish community will become accustomed to that energy source.”
If the extra source of energy is suddenly eliminated, individual fish may struggle to compete for the smaller food supply and part of the population may starve. Fish communities accustomed to feeding programs often collapse into imbalance when feeding programs are cut off, making for a complicated and expensive problem for a farm pond owner to correct.
Feeding can last throughout the summer and fall, Jones said. Continue feeding on a regular schedule throughout the year until the fish stop eating in the early winter.
“After successfully implementing a fertilization or feeding program, pond owners should harvest fish from their pond on a regular basis in the summer and simply enjoy the benefits of bigger fish and fish populations,” he said.
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