I have a large 20 ft long concrete pond in florida. I used to have a major algae problem until I hooked up a uv sterilizer. It burns up the algae. Plants would work great, except they get gobbled up by aquatic turtles faster than they can grow. I still have a problem with organic sludge building up on the bottom. I have to vacuum it out regularly, which is a major pain.
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-Jake

1.1 juvie L.t. annulata
1.1 adult/subadult L.g. californiae
0.1 mexican double yellowheaded amazon parrot