Why don’t you just let it go “natural”?
I think like a biologist so I can appreciate this question and am always striving to create and maintain an environment that is as natural as possible. However, there is very little that’s natural about a man-made, shallow pond in sub-tropical South Florida. Our twelve month growing season and dependence on fertilizer to maintain the lush turf grass and tropical landscape, make some form of lake management necessary. Non-native aquatic weeds have an amazing capacity to out compete natives and quickly overgrow lakes and wetlands. In many cases, you would not be able to see water without the efforts of your “lake guy”. This is not an exaggeration: I have literally begun work on new sites where plant and algae growth completely obscured the water.
Does that hurt the fish?
This is, by far, the most commonly asked question in the field. It usually comes right after “What are you doing?”. The short answer is no. All of the materials that are labelled (legal) for aquatic use in Florida are heavily tested and have shown to provide a wide margin of safety for wildlife. However, the improper use of algaecides and herbicides can cause fish kills, mostly by being TOO effective. Rapid death and decomposition of algae or other aquatic plants can result in low levels of dissolved oxygen in the water and result in fish suffocation. In a water body with a large amount of unwanted growth, steps should be taken to avoid rapid decomposition of the entire bio-mass at the same time. Unintended consequences are the most important reason to seek out knowledgeable, experienced and licensed professionals.
What causes fish kills?
Most fish kills come about as a result of low oxygen levels in the water. One cause of low D.O. (dissolved oxygen) is described above, but this condition usually occurs because of a weather change or other natural phenomena.
The other most common cause of fish mortality is poisoning. Overuse of some aquatic herbicides can cause an environment too toxic for fish, but the greatest threat comes from run-off. Most lakes and ponds in South Florida are “retention ponds”, meaning they were created to retain storm water for flood control and irrigation. All run-off from roads, parking lots, landscaped and grassy areas ends up in the lake. Anything applied to those areas or dumped into a storm drain is a potential toxin to fish and other wildlife. Some of the most common culprits are the materials used to re-surface blacktop. the first question that I ask when investigating a fish kill is; “did you re-seal your parking lot?”
Is there a way to prevent algae?
There is no way to prevent algae and aquatic weed growth but you can limit it. The best thing that you can do for your lake is to lessen it’s nutrient load. As discussed above, your entire property, or that of your community, drains into the water and brings with it fertilizer and anything else that’s applied to your landscape. In addition, leaves, branches, and grass clippings from careless mowing all end up in the water, decompose, and add to the problem of high nutrient levels. This process is natural and inevitable, but anything that you can do to keep organic materials out of the water is a good thing. Local cities and counties have enacted policies/ordinances to encourage water-friendly fertilizer use. The Palm Beach County ordinance can be found here:
Palm Beach County Fertilizer Ordinance
It is also recommended that only phosphate free products are used when fertilizing turf. Your grass doesn’t need phosphates and it is a large contributor to algae growth. The 3 numbers on a bag of fertilizer represent the primary nutrients, nitrogen, phosphorous and potassium. If the middle number is 0 (eg.20-0-10), it’s phosphate free. If possible, ALL fertilizer use should be curtailed during the rainy season.
You may see treatments being performed when algae growth is not obvious, and some will call that a “preventative treatment”. Algae is nearly always present at some level, and will start in the shallow, near shore, areas where sunlight reaches the bottom, so a light treatment near the bank can sometimes prevent a bigger problem later.
Do you ever see alligators?
YES. Alligators are far more common than most people realize and are an important part of the aquatic ecosystem. If you have an alligator in your waterway, consider yourself lucky. In most cases, they do not represent a threat to humans and are a source of great fascination for your out-of-town guests. Late March through June is alligator mating season. Early in that season is when you are most likely to see gators in unusual places (like your swimming pool or your front porch). These are males that are out looking for love or those that have been forced out of the territory of a more dominant male. Later in the season, females can be more aggressive because they are protecting a nest, but nests are usually in remote areas (likely not in your golf course community). Obviously, it is a good idea to keep your children and pets away from the waters edge, especially during dusk and night hours. If you believe that an alligator is becoming dangerous, for example it frequents an area where children play, you should call the Nuisance Alligator Hotline 866-FWC-Gator (866-392-4286). The Florida Wildlife Commission has specific criteria to determine whether they consider an alligator to be a problem. Keep in mind that nuisance alligators are killed (not relocated). Don’t take matters in you own hands as state law prohibits killing, harassing or possessing alligators
