This is the basic sequence of events leading up to pond scum and lake weed problems. It should be noted that not all problems arise from these causes. There are problems related to the over fertilization of a body of water which can lead to some of the same results. There are tell tale signs which can be easily seen by checking water clarity. If the water is a virtual soup of green suspended algae, the water is too fertile, and other measures, like adding vegetation to the intake side to filter some of the nutrients should be taken. While this does happen, it occurs so infrequently that I have seen only one or two cases in my life.
Sequence of events resulting in pond scum and lake weed problems:
- There is not enough fertility
- Water becomes too clear
- Sunlight penetrates to the bottom
- Sunlight warms the bottom
- Weed and algae germination and growth is initiated
- Weeds quickly grow through the water profile
- Filamentous algae begins to rise from the bottom
- Weeds and pond scum become the dominate feature of the lake or pond
- Fishing and recreational use becomes difficult
- Mosquitoes arrive and decide they like the surroundings
- Water quality worsens
- Dissolved oxygen is low in the evenings
- Fish rise to the top to gulp oxygen close to the surface
- Without plankton, the life cycle is slowed and the fish become hungry and skinny
The last problem listed in this sequence has probably been a problem for a while. Phytoplankton is needed in the water to:
Color the water for sunlight control
By coloring the pond or lake water, sunlight is prevented from reaching the lake bed where weeds and filamentous algae get their start. This provides lake weed and pond scum prevention.
Shade the water for heat control
By shading the water, the temperatures are moderated, providing better, more comfortable conditions for aquatic life.
Produce oxygen throughout the water profile
With higher oxygen production in the water, fish are able to breathe easy, and concentrate on avoiding predation, and food intake.
Provide food for the life chain
Because phytoplankton is the beginning of the "circle of life", food for fish is produced as a natural result.
Producing phytoplankton, or algae bloom is pretty easy to do, but there are a few preliminaries. You can read more about them: Pond Scum Prevention Pond Algae
