Below is general information about deploying SolarBee and GridBee circulators for epilimnetic applications. To the left, the "Compare Flows" link graphically shows how SolarBees are deployed for epilimnetic treatment, and there are other links for more in-depth lake information.

Summer stratification:  Starting in the spring and continuing into the summer, intense sunlight causes most lakes to "stratify" into a layer of warm less-dense water at the top of the lake, called the epilimnion, and cooler more-dense water at the bottom of the lake, called the hypolimnion. 

Typical epilimnion:  Almost all algae and other plant growth occurs in the epilimnion, because the light is strong enough there for photosynthesis. In most of the hundreds of lakes we have tested, the epilimnion comprises the top 5 ft to 10 feet of the lake, though in some lakes it can extend deeper. The "thermocline" is the boundary between the warmer epilimnion and cooler hypolimnion below, and you can often feel the temperature change at the thermocline with your feet while swimming. Usually the depth of the thermocline is about twice the  "Secchi depth".  So if the clarity is 4 ft deep, as measured with a Secchi disc, usually the thermocline is at 8 ft deep.

The problem with HABS: The most serious lake problem in the epilimnion is blue-green algae (cyanobacteria) blooms, often called HABs (harmful algae blooms). HABs often produce potent toxins  (there are about 100 different ones) and odors, and also cause high pH,  low DO (dissolved oxygen) at night, and fish kills. HAB toxins pose a very serious threat to human and animal health, and can cause death shortly after ingestion. In less severe cases,  a human can swim in a lake with a HAB, and then, years later, discover the HAB caused serious liver damage, with symptoms similar to many different diseases, including diseases commonly associated with over-exposure to mold. 

Good algae early in the season: Typically in spring, and all year long in a healthy lake, harmless bacteria and small-celled "edible" green algae and diatoms dominate in the epilimnion. These algae are too small to see with the naked eye, they just impart a clear tint to the water, and these algae never become out of control because zooplankton constantly graze on them. The result is that the main nutrients in the water (carbon, nitrogen, phosphorus) go all the way up the food chain (from good algae to zooplankton to fish), and the lake remains clear and healthy.   

Blue-green algae, usually in summer: A problem with "good" algae is that it is planktonic (goes with the flow of the water, no self propulsion). And it weighs slightly more than water, so it is always sinking out of the light unless wind-mixing re-suspends it. So at some point in the summer, in many lakes, an opportunity is created for blue-green algae to become dominant in the lake, especially during periods of low wind, hot weather, or high nutrient input. Blue-green algae have many competitive advantages to help obtain and maintain domination of the lake for the rest of the season. Depending on the species, these advantages can include: being too large for most zooplankton to eat, emission of toxins that can kill predators, the ability to form surface scums and long chains of molecules to avoid predators and shade out other algae from the sun, the ability to adjust buoyancy to descend to the bottom for nutrients and the ascend back to the top for sunlight, excess phosphorus uptake and storage capacity, the ability to utilize nitrogen gas from the air, the ability to affect reproduction to optimize the success of future generations, and other advantages.

"Stir the beaker": It has long been known that if epilimnetic water is "stirred"  in a beaker, the "good" algae will dominate, and blue-green algae will not become established. But, prior to SolarBee, no in-lake machine could mix  more than about one surface acre of the epilimnion of a lake with strong enough mixing to defeat blue-green algae. What makes SolarBee circulators unique is that our patented technology takes advantage of how water forms thin layers in a reservoir, which allows each large machine to mix about 35-40 surface acres of the lake epilimnion in a manner strong enough to defeat blue-green algae, and while using just solar power.

Mechanisms for blue-green algae control: SolarBee circulators are controlling blue-green algae in about 350 lakes in the US, most of which are documented in the customer experience database on this website.  Many of these projects are now 5-10 years old, demonstrating the permanency of the solution. About 50% of these lakes provide source water for drinking water plants, and the drinking water plant has good before-after records which show how much the lake improved. But while the beneficial results are undisputable, the exact mechanism by which blue-green algae control occurs has been the subject of much discussion, both inside and outside of our company. The answer probably involves one or more of the below four mechanisms, acting alone or together to various degrees, in various lakes. The below description of the likely mechanisms was "lifted" from the "Common Sense. . . . "  lake paper available on this website.

  • (a) The "good" edible planktonic algae which have sunk 5-10 feet down from the surface, and are at the verge of sinking out of the light and dying, are constantly being pulled into the SolarBee intake,  (radially from all directions, at a depth of the SolarBee intake plate which is usually 5-10 ft deep)  and lifted up to the top of the lake, and then spread out radially across the top of the lake.  This gives them new access to light and nutrients, and takes away the buoyancy-adjusting advantage of blue-green algae, and may allow good algae and natural bacteria in the water to out-compete blue-green algae for available P and N.
  • (b) The SolarBee mixing creates  a strong ongoing crop of good algae and bacteria all summer long that results in more and larger zooplankton in the lake which, when necessary for survival, will eat blue-green algae in addition to cropping down the good algae.
  • (c) When water enters the SolarBee intake hose at 3,000 gpm, just above the horizontal intake plate say at 5-10 ft. deep, and is popped up to the surface in a just a few seconds, the sudden reduction in water pressure on the blue-green algae cells, which were constantly adjusting their buoyancy, may cause the cells to become so buoyant that they are "stuck" in the water tension and surface film at the top of the lake, where they die or are killed by the sun. (This effect can also be seen in water samples drawn from 5-10 ft deep in a lake and placed into a sample bottle; due to the sudden pressure reduction the blue-green algae will usually pop up to the top of the water sample bottle in a few hours, and remain there to die.)  If this is occurring every day of the year, the blue-green algae may never get the population traction which is needed to create a bloom.
  • (d) The SolarBee radial mixing pattern, both the inflow and outflow of the machine, may be more effective than natural wind mixing in distributing cyanophages (viruses of blue-green algae) and other natural microbial control agents of blue-green algae, throughout the epilimnion of the lake. With the blue-green algae constantly being killed, harmless bacteria and "good" algae are dominant in the lake all year.

Weeds:  Another lake problem in the epilimnion is invasive macrophytes (weeds) in the littoral zone, the shallow area near shore where the sun penetrates all the way to the sediment. One common example is Eurasian Watermilfoil. Invasive macrophytes are not toxic, but can be a nuisance for swimming and boating, as well as helping to create conditions that allow HABs to thrive near the shore. Usually SolarBee circulation will slowly reverse lightly-rooted invasives while helping deeper-rooted native plant species remain dominant. This is possibly due to SolarBee circulation increasing the biological oxidation of the ammonia in littoral sediments to nitrate, which is not as readily usable by macrophytes. More information is available on this subject in the "papers" section of this website.

Summary of Benefits of SolarBee Epilimnetic Circulation:

  • Prevent and control harmful cyanobacteria (blue-green algae) blooms
  • Reduce taste and odor problems in drinking water
  • Reduce public health issues associated with cyanotoxins
  • Reduce pH and total organic carbon (TOC) levels
  • Prevent noxious odors and aesthetic impairment
  • Prevent surface water stagnation
  • Reduce fecal coliforms through greater exposure to solar UV radiation
  • Improve water clarity
  • Improve dissolved oxygen (DO) distribution
  • Improve fish habitats and aquatic biodiversity
  • Enhance compaction and muck reduction of near-shore sediments
  • Reduce growth of filamentous algae
  • Reduce growth of invasive aquatic weeds
  • Minimize or eliminate need for toxic algaecides and herbicides


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