Pond management and lake fertilization
There are times in the life of a pond or lake when clearing the water may be necessary. At those times, there are flocking agents that will do the job well. You should be aware however, that a completely clear pond or lake is not the optimum circumstance for a healthy body of water. Unfortunately, there are many who suffer from the illusion of healthy happy fish in a beautiful crystal clear pond, but it is just that, an illusion! For healthy fish, and for a healthy pond ecosystem, there must be something growing in the water, and that something is phytoplankton. The way to get it is through fertilization.
Nowhere in the world of living things can the effects of fertilization be seen more clearly than in a pond or lake. The effect can be almost immediate, and often drastic. The results, if properly implemented, will be a near incredible increase in fish size and numbers. Properly timed and implemented fertilizer applications will also reduce the population of unwanted submersed and emergent weeds.
An analogy: Cattle pastures and fish ponds
Think of it in terms of a cattle pasture. If you fertilize the grass, the cattle will grow more quickly, and the pasture may be able to support more cows. Reproduction will increase, and pounds of milk or beef per acre will increase. Lake fertilization works the same way. Increased pond fertility will increase the food source for your fish, which will increase their size and numbers. If done properly, you will also cause the grasses to outgrow the weeds.
What kind of fertilizer and how much
Fertilization will produce algae bloom, or phytoplankton in your pond. The right fertilizer is a fertilizer high in phosphorous and low in the other 2 elements. Phosphorous is the middle number in the 3 numbers listed on a bag of fertilizer. You need to add 40 lbs of 20% phosphorous, or 20 lbs of 40% phosphorous, or something similar in ratio per acre to initiate algae bloom. It takes about 4 to 8 pounds of pure phosphorous to produce or maintain algae bloom in an acre of water. If you had a product with 80% active ingredient, you would need about 10 pounds. However you get there, you need about 8 pounds of the second number in the fertilizer label, and as little of the other ingredients as possible.
There are some great pond and lake fertilizers available, but if you can’t find them, regular old high phosphorous agricultural fertilizer granules can be used. There are also liquids available, but when using liquids in a pond or lake, always remember that the fertilizer is heavier than the pond water, and will sink to the bottom unless you add water before releasing it into the pond water.
An alternative to phosphorous for pond fertilization
With phosphorous being closely monitored today, and restrictions on the horizon, it may be a good idea to look into alternatives such as the ones mentioned in this post by Mr. Bhaskar on our Lake Advice Blog: Diatom Algae. For the details on various methods fertilize your pond see Pond Fertilization Methods . Find more information about the effects of lake fertilization throughout this site.