Florida Freshwater FAQ's


What are algae? Algae are a diverse group of organisms that photosynthesize, but lack the complexity of plants. The word ‘algae’ describes many different types of organisms from larger (macroscopic) things that look like plants to microscopic single-celled life forms and even bacteria. Although individual species can be very different, all algae share the common characteristic that they derive their energy from the sun.

What causes algae to bloom? Like any organism that has abundant resources, algae increase in numbers when they have everything in need. When exposed to the optimum levels of light, temperature, salinity and nutrients, algal growth increases so quickly that plumes of color (usually green) can be seen in the water.

Why do algae stick to my fountain? Some types of algae grow in the water column, while others need something on which to attach. Provided a substrate and water, algae can grow almost anywhere.


Can fish survive the plants taking over? Fish usually thrive in the presence of abundant plant growth. Plants contribute dissolved oxygen (DO) and shade/cover for fish. However, excessive plant growth can get in the way of catching and enjoying the fish, and presents safety problems to anyone who might fall into a twisted mass of plant growth. Similar to an algal bloom die off, a sudden die down of plants could cause an abrupt DO decline that might cause a fish kill. Plants should therefore be maintained at a manageable level, and those species that are not likely to overgrow should be encouraged.

Why are frogs suddenly taking over? An abundance of frogs might indicate a breeding event since adult frogs tend to assemble en masse to breed. Since many frogs return to breed at the same place they were born, you might observe repeated periodic migrations of frogs to and from your pond. On a positive note, populations of amphibians, such as frogs, are generally a sign of good water quality.

Why are the birds dying around my lake? Unless you see evidence that a bird has been hit by a car or electrocuted, bird deaths can be mysterious. Possible causes of bird deaths related to lakes include algal toxins or avian botulism. Both of these causes are relatively rare. If you are seeing large numbers of birds dying, you should report the problem right away. Bird deaths in Florida are handled by the Florida Fish and Wildlife Conservation Commission by filling out the form located at www.myfwc.com

Why are the fish dying? Low oxygen levels are the most common reason for fish kills. In Florida, this most commonly occurs in the fall and summer. When the weather is hot, water is not able to hold as much dissolved oxygen (DO) for the fish to breathe. Sudden drops in oxygen caused by dying algal blooms are common in summer, as bacteria use up all the oxygen while breaking down the dead algae. Couple this with already low DO levels, and fish can die quickly.

Fish kills in fall, usually in October, are caused by the sudden change in weather that causes lakes to mix (turnover), bringing up poorly oxygenated water from the depths. A much more rare cause of fish kills is a bloom of golden algae, which release a toxin that suffocates fish. As the name suggests, golden algae are not green, and the blooms are generally not visible. A lake management professional will try to determine the cause of your fish kill in order to try to prevent future occurrence.

Aquatic Plants

Why are grasses taking over my lake? Grasses are some of the fastest-growing plants, and have the ability to crowd out more desirable plants.

Why are lily pads taking over? Lilies and other pad-forming floating plants require specific water level conditions to grow, but they will thrive wherever those conditions are met, so you lake must be just the way they like it! Like any other plant, they require attention to ensure they grow at a manageable level.

Why are the plants taking over the whole lake? Like any organism that has abundant resources, plants increase in numbers when they have everything in need. When exposed to the optimum levels of light, temperature, salinity and nutrients, plants continue to grow until limited by one of these environmental factors. In lakes, noxious plant growth is usually a result of an overabundance of the nutrient phosphorus.


Why do we have so many man-made lakes in Florida? Both retention and detention ponds can and should function as healthy eco-systems and with proper planning and maintenance can enhance the livability of the area in which they exist but they are created for three main reasons:

  • Water Management: Whether generating power, controlling flooding or for navigation or drinking water; humans have been building dams to create reservoirs for centuries. A detention pond is a low lying area that is designed to temporarily hold a set amount of water while slowly draining to another location. They are more or less around for flood control when large amounts of rain could cause flash flooding if not dealt with properly.
  • Control pollution: A retention pond is designed to hold a specific amount of water indefinitely. Usually the pond is designed to have drainage leading to another location when the water level gets above the pond capacity, but still maintains a certain capacity. These ponds are created to prevent deterioration of natural freshwater bodies from nutrient and pollutant laden water that drains from paved roads and yards.
  • Aesthetics to Improved Home Values: Water views add real estate “value”. From the smallest backyard koi pond to ponds sprinkled throughout a golf course, to large lakes built as part of a planned 'waterfront' community; these bodies of water are built to provide outdoor activities and enjoyment.

I have dark clumps, is it algae? Maybe… Clumps of material floating on top of the water or lying at the bottom can be a number of things, including algae, plants, or runoff debris such as grass clippings. A lake management professional can usually identify the cause of any unsightly ‘clumps’ in the water.

What is the green stuff taking over my lake? If there is green stuff taking over your lake, you probably have an algae or plant problem. Both types of organisms can form dense green mats that float on top of the water. Some tiny floating plants, like duckweed or watermeal, look like algae scums at first glance. In addition to surface growth, algal blooms can turn the whole water column green. These types of problems suggest a nutrient problem, usually an over-abundance of phosphorus that allow the plant material to grow out of control.

Why does my lake smell bad? A healthy lake should not smell bad, but there are many reasons why a lake might periodically smell unpleasant. Stagnant, poorly oxygenated water contains bacteria that create hydrogen sulfide gas, which gives the water a rotten-egg smell. Often that poorly oxygenated water is hidden several feet under the surface, and the water smells fine.

Windy, cooler weather can cause a lake to mix, which brings the bad water to the surface where we can suddenly smell it. In Florida, this most commonly occurs in October, right after our first cold front, but episodes of foul smelling water are common throughout the warmer months of the summer and fall. During aeration startup, a lake is forced to mix in any weather, so a temporary bad smell is expected. However, once the bad smelling gasses are released, aeration prevents them from re-forming. Other sources of stink near your lake include algal blooms and dead organisms (including plants or fish).

Why does my pond have muck? Where do all of the runoff and dead algae and plants go when they are no longer visible in the water? They fall to the bottom of the lake and become sediment. Sediments that are made up of mostly dead organic material are called muck, which has a thick sticky texture, and often has an unpleasant rotten-egg sulfur smell. Because muck is organic, it can contribute nutrients back to the water, causing algal bloom, clarity, and odor problems in the lake.

Why is my pond scummy? Ponds can have a variety of floating scums. Sometimes floating algae and plants are referred to as scum. Oil and gas scums create a rainbow sheen on top of the water. Foamy or bubbly scums can be a sign of soap pollution in the water. Sometimes a lake management technician might take a water or scum sample for later analysis and/or identification.

Why is my pond water green? Microscopic planktonic (floating) algae can grow in various levels in the water, making the water itself appear green.

Why is the lake water so low? In Florida, low water is typically caused by either dry weather or management activity. Many of our lakes are connected either underground or by canals to larger water bodies. Drought or draw-down can cause lake levels to decline seemingly overnight.

Water Testing

Can you test for dissolved oxygen (DO)? The best way to test for dissolved oxygen (DO) is with an on-site test kit since the oxygen in the water can rapidly change if the water is transported. We often test for DO before algae treatments or after fish kills to determine if oxygen levels are as high as they should be. Sometimes we use an electronic meter to test DO at different depths in the lake because the water at the bottom of the lake may lack oxygen despite abundant oxygen at the surface. This is called stratification, and it can mask overall low DO in the lake water that may result in a fish kill later on.

Do you test for salt? Even freshwater can contain some salt, so we test the water’s specific conductivity. This parameter can detect imperceptible levels of salt, and gives us a good idea of what kinds of fish and plants will grow in lake, as well as letting you know if the water is safe for irrigation. Changes in specific conductivity can be indicative of seasonal changes or pollution.

What is good water chemistry? When water chemistry is good, it is easier to keep your lake in good condition. We will occasionally track the water chemistry in difficult lakes. For more information on what makes good water chemistry download the Water Chemistry PDF