05/11/2026
When Fertilization is Appropriate for Fishing Ponds
One of the many characteristics landowners can manipulate with their ponds is water fertility. Done correctly, fertilization can boost fish populations, growth rates, and maximum size. Done carelessly, fertilization can intensify w**d problems, throw fish communities out of balance, and lead to oxygen problems, toxic algae, and fish kills.
Should You Fertilize
Most Arkansas pond owners should not be fertilizing their ponds. Much of the state has naturally fertile soil. You should only consider fertilization if you are motivated and able to harvest twice as many fish as typically recommended and can commit to maintaining the fertilization program indefinitely. Short-term fertilization is most often a waste of money, and abruptly ending fertilization after it has been provided for several months to years can wreck fish population balances that have become accustomed to it. Certain pond characteristics also make fertilization inappropriate. Do not fertilize if 1) the pond is consistently muddy, 2) a dense plankton bloom already exists, 3) aquatic w**ds are already established, 4) water flow through the pond is consistently high, 5) sunlight does not reach the pond, or 6) you are already applying fish feed daily. Fertilizing in these situations is at best a waste of money and at worst detrimental to the health of the pond.
Fertilizer Types
The two broadest categories of fertilizer are organic and inorganic. Organic fertilizers like alfalfa and cottonseed meal are relatively low in nutrient content compared to inorganic fertilizers. They also must decompose before the nutrients are available to plankton. This decomposition consumes oxygen and can lead to fish kills if overapplied. Organic fertilizers are acceptable for new and renovated ponds, but risky for ponds already containing fish. Inorganic fertilizers are more commonly used for ponds because they produce plankton blooms much faster, have more concentrated and consistent nutrient content, and present lower risks of oxygen problems. Pond fertilizers come in powdered, liquid and granular forms.
Application Techniques and Rates
Powdered fertilizers tend to be the easiest to apply. Simply open the bag and spread it around the surface of the pond or sprinkle it into the prop wash of a boat traveling around the pond. Liquid fertilizers produce blooms the fastest, but they must be diluted according to label instructions before applying them to the pond. Liquid fertilizers are highly concentrated, making them much denser than normal water. If applied to the pond straight from the jug with no dilution, the fertilizer will quickly sink and stay near the pond bottom. This is wasteful because the plankton we are trying to feed stay near the pond’s surface. Granular fertilizer also should not be applied straight to the pond. The granules sink to the bottom where they slowly dissolve. Much of the nutrients become trapped in the sediment, wasting the fertilizer. One way you can effectively use granulated fertilizer is to build a submerged platform within about 1 foot of the water’s surface to pour the fertilizer on. Another trick is to simply lay the fertilizer bag in the water near shore and cut an “X” into the upper side of the bag. These approaches allow wave action and currents to slowly dissolve the fertilizer near the water’s surface without losing it to the bottom mud.
Each fertilizer has a three number rating system called the NPK ratio representing the ratio of nitrogen (N), phosphorous (P), and potassium (K) contained in the product. Newly built ponds are often deficient in nitrogen and phosphorous. Potassium is rarely limiting plankton blooms and is therefore often low to absent in pond fertilizers. Beginning with a 10-10-10, 20-10-0, 20-20-5, or similar fertilizer can help plankton blooms establish in new ponds faster than a phosphorous-heavy blend. When the water reaches 60°F in the spring, apply about 20 pounds per acre of these fertilizers every two weeks until the pond produces a plankton bloom that reduces water visibility to less than 24 inches (Figure 1). Once the bloom is established, shift to a phosphorous-heavy fertilizer like 10-34-0, 12-48-0, 0-46-0, or similar, and apply 4 to 8 pounds, or 0.5 to 1.0 gallon for liquid formulations, per acre only when the water clears to more than 24 inches of visibility. As the pond ages, you will likely need less fertilizer to initiate and maintain blooms. For older ponds, you can begin and maintain blooms with phosphorous-heavy blends as nitrogen supplies within the pond are usually sufficient.
Monitoring the Bloom
The “Secchi disk” is a tool used by casual and professional pond managers to measure water clarity (Figure 2). It is simply a flat disk painted in alternating contrasting colors lowered into the water at the end of a measured stick or pipe until the disk is no longer visible. The depth at which the disk disappears is recorded as the “Secchi depth.” Ideal plankton bloom density will produce a Secchi depth of 18 to 24 inches. Do not fertilize until the Secchi depth has increased to more than 24 inches.
What to Watch Out for in April:
Aquatic w**ds are growing now; herbicide applications are generally effective this time of year. DIY plant ID resources can be found at Texas A&M’s Aquaplant “Identify a Plant” directory https://aquaplant.tamu.edu/. The MP556 (https://www.uaex.uada.edu/publications/pdf/MP556.pdf) contains photos of most common problematic aquatic w**ds in Arkansas along with management guidance. There is also an aquatics section in MP44, covering herbicide selection and precautions.
Pond Management Tasks for April:
Fertilization and feeding programs should be underway. It is time for aquatic dye for w**d/algae control. Be aware that during the rainy season dyes will need to be reapplied regularly to maintain effective concentration. Begin herbicide applications for troublesome w**ds. This is a favorable time for fish stocking (species and numbers depend on the client’s situation and pond conditions). Now that weather is nice, people will resume fishing so harvesting largemouth bass (10-15 lbs/acre/yr for normal ponds, 25-35 lbs/acre/yr for bass-crowded or highly productive ponds) is encouraged. Harvest of bluegill less than about 7 inches in length up to about 25 lbs/acre/yr is acceptable. Aggressive harvest of all crappie caught, especially from ponds smaller than about 25 acres is encouraged. Crappie are s*xually mature at about 6 inches and can spawn prolifically (often resulting in overpopulation in small ponds) so aggressive harvest of eating-size crappie often does not result in crippling the spawning capabilities of the fishery. Begin mowing grass on dams and levees to keep brush and saplings from developing. Keep drains and spillways clear of debris and clogs so that they are working efficiently during the rainy season. Turn on aerators if they have been off for the winter. For diffused aeration systems, follow the startup schedule of: Day 1, run 30 minutes then turn it off the rest of the day. Day 2, run 1 hour. Day 3, run 2 hours. Day 4, run 4 hours. Continue doubling the run time each day.
Scott Jones
Small Impoundment Extension Specialist / Instructor II
Department of Aquaculture and Fisheries
University of Arkansas Pine Bluff