g-8-outdoors, If I read your request properly, you have actually have three questions.
Question 1: "will aeration help prevent the algae bloom?"
Some ponds age quicker than normal. This usually due to low assimilation ability of the pond. In other words, there are not enough beneficial organisms to consume the ortho-phosphates, nitrates, and other nutrients that are entering the pond from your watershed and from your well. You may even be feeding too. This is due to low oxygen levels typically found at the bottom of the pond.
By increasing the oxygen levels from top to bottom, an organism (zooplankton) now has a larger area to feed. Zooplankton is one of the largest consumers of plankton algae in a pond. They are also the basis of the food chain for fish.
Also, once an aeration system is installed in a pond, the oxygen levels are raised at the bottom, the habitat for beneficial bacteria (aerobic bacteria) and benthic organisms (slugs, snails, mussels, worms) will begin to move throughout the entire pond bottom and begin to consume that muck layer.
Other things happen to help limit the release of nutrients in the water column. One measurement we use as Limnologist is called the Redox Potential. This is a measure of the proportion of oxidation to reduce substances. In a pond that is low in oxygen or (anaerobic) the redox typically is in the negatives. Once we aerate, the redox now turns to the positive thereby bonding the orthophosphorous and nitrates to the bottom of the pond and limiting the release for the algae to use as a food source. Also iron found in the water column will precipitate out of the water column and act as a blanket on the bottom blocking the release of these nutrients.
In summary, by adding an aeration system we have now increased the pond's ability to assimilate the nutrients that are washing in.
Question 2: "Can I get away with not pumping in well water during the summer months and just let the average depth of the pond be lower to where the lake has an average depth of about 3 feet"
Answer: I would recomend keeping as deep a water depth as possible to a) reduce the depth by which the sun can penetrate thereby reducing the plankton algae's ability to produce chlorophyll, b) to limit predation by birds. With that shallow of a depth, you could find that you loose more fish due to avian predation.
The algae bloom found when you run the pump is due to the combination of as stated above, accessive nutrients washing in from the watershed and the internal nutrient loading from the well. Again, the lake does not have the abilty or capacity to assimilate those nutrients due to increased anoxic areas in the bottom. Aeration will aid in elimnating those problems.
Question 3: "We have a fish kill about every 5 years or so"
Answer: I know that this is not a question, but I am sure you want to elimnate the possibility of any further oxygen related fish kills.
Aeration will eliminate this. That large algae bloom you spoke of will generate large amounts of oxygen during the day at the surface. At night, that same large algae bloom will respirate and consume that same oxygen. That action combined with the lack of oxygen found at the bottom and the fact that the fish & bacteria need oxygen during the night too will drop the oxygen levels so low that the fish are unable to survive.
Just from the limited information you provided on the size in acres of your lake and the average depth, (6) well placed AirStations will solve these problems for you. Please feel free to contact me to discuss this further. I feel this forum is spectacular for information gathering and question answering, but I also would like to make sure your concerns and questions are taken care of.
I look forward to hearing from you.
Ted, thank you for bringing this to my attention.
