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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Algae scrubber | 1/3 | https://en.wikipedia.org/wiki/Algae_scrubber | reference | science, encyclopedia | 2026-05-05T09:00:37.646457+00:00 | kb-cron |
An algae scrubber is a water filtering device which uses light to grow algae; in this process, undesirable chemicals are removed from the water. Algae scrubbers allow hobbyists to operate their saltwater or freshwater tanks or ponds using natural filtration based on primary production, much as occurs in oceans and lakes.
== Concepts == An algae scrubber filters water by moving water rapidly over a rough, highly illuminated surface, which causes algae to start growing in large amounts. As the algae grow, they consume nutrients such as nitrate, phosphate, nitrite, ammonia, ammonium and even metals such as copper from the water. These nutrients are normally a problem in aquariums and ponds because they cause nuisance algae to grow, and also because they cause sickness and/or other problems in aquarium fish, invertebrates and corals. An algae scrubber allows algae to grow, but the algae grow inside the filter instead of in the aquarium or pond. This removes excess nutrients (scrubs the water), diminishing nuisance algae in the aquarium or pond . Nuisance algae in the aquarium or pond are not to be confused with the desired algae in the algae scrubber filter itself. The algae that grow in the algae scrubber can then be removed, or fed back to the livestock. Both iron fertilization and ocean nourishment are techniques that boost the primary production of algae in the ocean, which consumes massive amounts of nutrients and CO2. It is this same consumption of nutrients that algae perform in an aquarium or pond. Algae scrubbers are used in both saltwater and freshwater, and remove nuisance algae of multiple types: cyano or slime, bubble, hair, Chaetomorpha, Caulerpa, and film algae, as well as dinoflagellates and Aiptasia.
== History ==
The algae scrubber was invented by Dr. Walter Adey, who beginning in the late 1970s, was Director of the Marine Systems Laboratory at the Museum of Natural History, Smithsonian Institution (Washington DC, USA). His research of various types of algae, especially in their ecological role on coral reefs, gave him insight into how the ocean (in particular a reef) "recycles" nutrients. He designed and built various exhibits ranging in size up to 3000 gallons, and modeled different aquatic ecological systems including a tropical coral reef/lagoon which "after 8 years of closure [to the environment], had its chemical parameters controlled solely by an algal turf scrubber. This system, studied by a multidisciplinary team of biologists, demonstrated calcification [coral growth] rates equal to the best 4 percent of wild reefs, and at 543 identified species, and an estimated 800 species, ranked per unit area as the most biodiverse reef ever measured." In three editions of his book, Dynamic Aquaria, Dr Adey described his work in detail and discussed in scientific principles the physical, chemical, and biological considerations for building a functioning ecological system within an enclosure, from aquarium size, to microcosm (up to 5000 gallons), or mesocosm size (>5000 gallons). In describing the algal turf scrubber he designed, he explained that removing excess nutrients was not its only function. By operating the scrubber at night when the main tank had shifted to a different respiratory phase (plants were now absorbing oxygen rather than producing it) the scrubber maintained oxygen levels and helped buffer pH by preventing high levels of carbon dioxide from building up.
"Recycling" means how the nutrients go from plants to animals, and back to plants again. On land, you see recycling by following the oxygen flow: Green plants use carbon dioxide and release oxygen; animals use this oxygen and release carbon dioxide. In oceans and lakes, the nutrients go from algae to animals, and back to the algae again.