What kind of fertilizer should I use in my pond?

Fertilizers suitable for farm pond use are available in liquid or granular form. Liquids are generally cheaper than granules and are superior in promoting phytoplankton growth in ponds. Granular fertilizers, however, may be more readily available than liquids in some areas. Phosphorus (P) is the most important nutrient in pond fertilizers and usually gives a much greater increase in fish production than nitrogen or potassium. An ideal farm pond fertilizer application should contain 4 to 8 pounds of phosphorus and 2 to 4 pounds of nitrogen per surface acre.
Concentrated liquid fertilizer may be sprayed over the shallow water edges of ponds with a power sprayer. A handheld garden sprayer can be used on the edge of small ponds. For small ponds (1 acre and less), liquid fertilizer can be diluted by mixing with 10 parts water and splashed over the pond surface. Do not pour liquid fertilizers directly into ponds because they are heavier than water and will flow to the bottom and not mix well.
Granular fertilizers should be kept from direct contact with pond mud if possible because the nutrients become trapped in the mud and are not available to the plankton. A fertilizer platform positioned just under the water surface keeps fertilizer off the bottom, allowing it to dissolve slowly into the water. A platform with a surface area of 45 square feet is sufficient for every 5 to 10 acres of pond surface. In some instances, bags of fertilizer may be placed directly in shallow water and cut open, allowing natural wave action to dissipate the fertilizer as it dissolves. Formulations for granular fertilizer vary widely, but a typical starting dose should provide approximately 8 pounds of phosphorus (P) per surface acre. The N-P-K (nitrogen-phosphorus-potassium) content will be listed in that order. Each number indicates the percentage of weight of each nutrient. An example of a complete fertilizer is 8-8-8, which contains by weight 8 percent N, 8 percent P, and 8 percent K. In other words, a 100-pound bag of 8-8-8 contains 8 pounds of each nutrient.