Lake Fertilization

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.

How To Fertilize A Pond Or Lake

 

So, you have had a few problems with your pond or lake that seem to indicate that you need a little extra fertility. Maybe what tipped you off was:

  • Poor fishing
  • Skinny fish
  • Low fish population
  • Excessive pond algae like blanket weed or pond scum
  • Excessive lake weed growth

Whatever it was that tipped you off, you have come to the conclusion that something has to be done to increase fish production, get rid of lake weeds and pond scum, and prevent these problems in the future.

  • You have done your homework.
  • You have tested the water clarity of your lake and solved any problems related to soil particles in the water.
  • You have checked the pH and corrected it if needed.
  • You have water which is too clear to support aquatic life, so you know that you need to produce algae bloom, and you know that that means you need to fertilize your lake.

How do you fertilize a pond or lake?

There are several suitable methods for pond and lake fertilization, but let me start off with a few cautionary statements.

Liquid pond fertilizer

Liquid fertilizer should be mixed with water before being applied to a lake or pond. The liquid fertilizer will be heavier than the water it is being applied to, and will sink to the bottom where it will probably either be neutralized, or initiate unwanted plant growth.

Keep fertilizer clear of outflow

If you are using buckets or platforms suspended in the water to slowly dissolve fertilizer, make sure that they are not close to your spillway or drain pipe. This could result in the majority of your fertilizer ending up downstream.

Simple pond fertilizer method

If you are using fertilizer in plastic bags, you can lay the bag in shallow water, 2 to 3 feet deep, and slit the top lengthwise and across to allow the fertilizer to dissolve.

Fertilizer platform

If you are using a submerged platform, the platform should be about 1 to 2 feet below the surface of the water, and the proper amount of granular fertilizer can be dumped onto the platform and allowed to dissolve at it’s own rate.

Fertilizer in a bucket

The same result can be attained by suspending a 5 gallon bucket full of fertilizer with small holes drilled into the sides from a dock. be sure that it is one to 2 feet deep.

Fertilizer products formulated for ponds and lakes

There are a lot of newer fertilizer products on the market specifically designed for pond and lake fertilization that offer other options such as finely ground granules. These products come with instructions and label directions.

Special aquatic weed control note:

It is important to start fertilization early in the spring. If algae bloom is in place before weeds and filamentous pond algae have a chance to get started, this will decrease the amount of weed control needed for the pond. See also: Lake Fertilization