Pond Boss Forums INTRO Questions & Observations Why is My Pond Water Green??

Why Is My Pond Water Green? and What Can I Do to get it Clear?

I have a small pond maybe 80' long x 50' across about 5-6 foot deep. I have my Aerator running 24-7

thanks for the help

the green color is probably phytoplankton. it is a microscopic algae. if you do some researh here and on the web you should be able to learn as much about this tiny plant as you can stomach. It is possible that your aerator is stirring up the bottom "muck". this muck is rich in nutrients and can cause a plankton bloom. if you have a diffuser type aerator you may consider moving it off the bottom. there are some bacteria treatments available on the market that will use up some of the nutrients. check these out as well

I would not recommend using a copper based herbicide for plankton control, especially in such a small pond.

phytoplankton will bloom even with cold water temps?? and I just changed my Diffusure!! Damn!! thanks for the info

shan leads you to believe that phytoplankton is one type or specie of tiny plant. Actually it a whole community of species (many species) often easily as many as 30 to 50 species growing suspended in the water column in one pond. A typical north-temperate lake can have several hundred algal species comprising the phytoplankton community (Kalff&Knoechel,1978). Another extreme was noted by Lange-Bertalot&Meltzin 1996 who identified over 800 algal taxa from just three lakes in northern Europe! So what you probably have is several to numerous different species living as a group suspended in your pondwater. However very likely only one or several are real abundant, the others have rare to scarce occurrance. The prevaling conditions will depend on who are abundant at any given time. Abundances of the different species varies greatly throughout the year again depending on the prevailing conditions. Each species has its own set of conditions that allows it to become abundant. Natures Way.

Running the aerator or at least the conditions being produced by the aerator may favor the current phytoplankton group. Without examining the water for species composition there is no way to be sure what you have. We can only generalize or guess.

As shan says the current operationg conditions of the aerator may be stimulating nutrient production & enriching the phytoplankton. ALSO Internal or External nutrient sources may be feeding it (fertilizer run off from the grass). Different species like different nutrient conditions or concentrations.

Anyway that is what is making your water green. Very likely at least millions of cells per ounce of water. The phytoplankton feeds the zooplankton; so with green water the zooplankton numbers are also high. Zooplankton feed baby or small fish. A few types of adult fish can also eat zooplankton.

How clear do you want your water? Are you willing to sacrifice fish growth and abundance for clear water? The theme here is to fertilize the water to MAKE it green and grow lots of big fish, although that is not the goal of everyone here.

PS It is a common myth perpetuated by aerator sales people that an aerator will produce clear water. Did someone lead you to believe the aerator would clear your water and if not why run 24/7? Obviously it did not hold true in your case! and a lot of other cases!

Bill,

Good call, I did not mean to make phytoplankton sound like one type of plant (but did)

last year I was called out on a fish kill. the pond was very small maybe 1/10th of an acre. it was dug out for irrigation and was very deep. the pond owner was sold an aerator by a salesman that lead him to believe many non-truths. It was a diffuser type aerator. this was the wrong pond for that type of aerator as there was much more water under the thromocline than above. the aerator broke down the stratification as advertized but did not provide enough oxygen to keep fish alive. We turned off the aerator, oxygen levels went back up naturally and fish were happy once again.

Two questions
If you run a bottom diffuser arreator starting before the formation of the thermocline will it be okay in a lake like that? Or is it never a good idea?

Second, How deep does something need to be to stratify, and what are some other factors in stratification?

Thanks Bill !! Damn You Have an abundance of Knowledge! I talked with my Local Fisheries Biologist and she recommended running the aerator just at night... I had a pretty high fish loss this winter and after talking to her(biologist) she reccomended running the aerator constant to help remove any unwanted gases that may have accumulated from the dead fish. Then once the Vegitation starts to grow just return to running it at night. She also recommended a few pounds of Fathead Minnows, as they breed often and would feed on the "green" and then in return feed the larger fish...

wht89lx - Once you provide the correct info we now know why the water is green. Most of the nutrients are coming from decompostion of dead fish. Ssome of the fish go to the bottom and decay there and do not float.

Ms fisheries biologist is not completely correct in leading you to believe the offspring from the fathead minnows will eat the phytoplankton bloom. The fathead fry will for a few days eat the unicellular and some colonial planktonic algae but they quickly switch to eating rotifers and small crustaceans. Once the get to 1" -1.5" they are thiving on larger crustaceans and small invertebrates. The zooplankton (protozoans, rotifers, and crustaceans) are the primary grazers of the phytoplankton.

tyw33 & shan - I briefly discussed aerator start up (spring and mid to late summer or fall) inthe forum heading: Questions&Observations: "Aeration Question" by jbrockey; see my Mar 20,2003 post. Check it out and if you still have more questions post the question under the forum: Aeration and topic: Should I Aerate?. I will gladly provide additional details / answers / opinions. I don't want my aeration answers buried in the topic "why is my pondwater green". I had to search all over for my Mar 20 post; darn thing was in Q&O not Aeration - go figure.

I went to the forum heading: 'Aeration' and topic: 'Should I Aerate?' and posted a section about pond stratification.

I'll check it out. I dont have much experience with aerators as many of the ponds and lakes I care for are large. Placing aertators large enough would not be cost effective. I dont sell them nor do I want to. I can see their usefulness in northern ponds, very small ponds or for a specific problem. I'm not sold on there effectivness for general use.

Large lake aeration systems are expensive. I'm also not sure where the 'cut off' size is for pond size where it isn't practical to aerate. Numerous municipalities do it to maintain water quality for their large reservoirs. Just like everything else it depends on how deep your pockets are. Also once you have a massive fish kill of fish that it took years to produce it gives one a different perspective or outlook. Sometimes overall water quality comes into consideration when water use issues are impt.