This article is from the Aquaria: Plants FAQ, by multiple authors.
Please read the ALGAE SECTION of the DISEASE FAQ for details on
specific algaes and remedies. But to summarize, you can keep
algae-eating fish to munch on it, starve it for nutrients by adding
floating or fast-growing plants that consume nutrients faster than the
algae, harvest some plants and remove dying leaves often to take
nutrients out of the tank, reduce feeding (or increase water changes
if you must overfeed), reduce the number of light hours per day, use
root fertilization instead of liquid leaf fertilization, or physically
remove it from the tank. There are also antibiotics for blue-green
algae and other algicides, but the latter can kill your plants as
well; use with caution!
 
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