re: What can be used to kill algae in a 14 acre pond?

Check the source of the runoff into your pond. May be getting too much nutrient material from a chicken lot, manure, or a heavily fertilized field?

I use a combination of Diquat E-PRO Aquatic Herbicide and pond dye for my 5 acre pond.
The pond dye helps with sunlight not getting to the bottom and allowing the deeper vegetation to grow. I use the diquat diluted in a 5 gallon sprayer. Do only one application at a time and allow it to work then do another portion of the pond. Have done it all summer and haven't had any issues with fish kills.

you can get both on amazon

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I am assuming plecos. Theyre sold as algae eaters but they dont do that at all.

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Yes, yes they do. Also, they will not live past November in La. in the wild. I have had them in a pond before. I no longer do it because I am too lazy to remove and care for them over winter.

Pond to shallow

15 feet too shallow??

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They are sometimes referred to as "janitor fish" among aquarists for their ability to clean tank algae.

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Exactly, theyre sold as janitor fish when they arent that at all. They are a net positive when it comes to the bio load in an aquarium.

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They are sometimes referred to as "janitor fish" among aquarists for their ability to clean tank algae.

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Exactly, theyre sold as janitor fish when they arent that at all. They are a net positive when it comes to the bio load in an aquarium.

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Except that isn't what you said. You said.

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theyre sold as algae eaters to people that dont know any better

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They are algae eaters.

Of course they are a net positive in terms of bioload, what living organism isn't? By eating algae the load they add provides a service by helping to keep the algae in check. They don't eliminate the need for filtration and will add to the filtration needed, obviously.

And the will get large, as I think you mentioned, so that has to be accounted for. Which I think may have been what you were getting at, that wasn't clear to me by what you initially posted. They can definitely get large enough and produce enough extra waste to tax the system if it is not properly sized to account for that additional waste. Then the algae eating benefit goes by the wayside.

Do you know what type of algae - planktonic, filamentous, etc.? Photos would be helpful. Not wise to treat a pond without specific identification of the type(s) of algae you are trying control. You may not get the control you desire and at great expense to yourself.

AquaPlant from Texas A&M is a good website for aquatic weed information and management if you are not familiar with it. LINK.

Labeled aquatic herbicides are going to safe in regards to their toxicity to alligators, turtles and fishes if used according to label directions, but of course the primary danger to the fish population is oxygen depletion after killing the algae and it decomposes, particularly during warm/hot summer months. Typically one needs to treat sections of the pond sequentially to minimize the potential occurrence oxygen depletion and subsequent fish kill.

You in Louisiana? If so, contact Dr. Chris Mudge LINK he is the aquatic weed research and extension specialist with the LSU AgCenter - Dr. Mudge is actually a federal employee with the US Army Corp of Engineers but holds an adjunct professor appointment with the Ag Center and is housed on main campus in Baton Rouge. He should be able to ID the algae for you and help you with appropriate treatment options.

The official recommendation I got from a professional pond management company said to use the copper stuff already mentioned here, but said to start using it before the algae becomes a problem, not in June/July. So, next year start the first application in April. Almost like a "pre-emergent" concept. For filamentous algae, that is.