Livestock can die from eating some algae. Such as Anabaena, Mycrocystis, Gloeotrichia etc.

When fish eat dinoflagellate algae in large quantities, toxic toxins are produced. Some algae cause gill disease in fish. eg Oedogonium

Some algae cause disease in tea, coffee, magnolia etc. plants and reduce the yield. eg Cephaleuros virescens.

A large amount of blue green algae (cyanobacteria) grows in pond or reservoir water, it is called water bloom or algal bloom. This pollutes the water in the reservoir and kills the fish. Such as Nostoc, Anabaena, Mycrocystis, Rivularia, Ocillatoria etc.

1. Water bloom: A large amount of blue green algae (cyanobacteria) grows in pond or reservoir water, it is called water bloom or algal bloom. This pollutes the water in the reservoir and kills the fish. Such as Nostoc, Anabaena, Mycrocystis, Rivularia, Ocillatoria etc.
2. Plant diseases: Some algae cause disease in tea, coffee, magnolia etc. plants and reduce the yield. eg Cephaleuros virescens.
3. Fish diseases: When fish eat dinoflagellate algae in large quantities, toxic toxins are produced. Some algae cause gill disease in fish. eg Oedogonium
4. Animal dead : Livestock can die from eating some algae. Such as Anabaena, Mycrocystis, Gloeotrichia etc.
5. Mosquito reproduction: Some algae provide nourishment to mosquito larvae and help increase mosquito population.
6. Photosynthesis hampers: Parasitic algae cover host plants and interfere with photosynthesis.
7. Walking problem: Blue green algae grows on roads and ponds making these places slippery. This causes difficulty in driving and accidents. Algae clogs the bottoms of various vessels and obstructs navigation.
8. Monument destroys : Damages walls and buildings by causing algae growth. As a result the stability of the installation is lost.
9. Malodor creation: malodorous substances are created from the cells of many algae. These substances pollute the environment.
10. Toxin creation: Gymnodinium and Microcystis algae produce harmful toxins. This toxin is harmful to fish and livestock. Harmful toxins produced by Gonyaulax algae accumulate in fish bodies. Eating this fish causes people to become paralyzed.

Mosquito larvae die in the presence of algae like Chara, Nitella etc. in water bodies. Mosquitoes can be controlled by cultivating these algae in water bodies.

Algae are widely used in the laboratory to prepare culture medium for bacteria and fungi.

A group of researchers from Dhaka University and Sweden’s Uppsala University have made nano filters from Pithophora algae. Nano filters are cellulose filters. It is like white paper and the pores of the filters are 17 nanometers. Waterborne microbes are 30-100 nanometers. So all viruses and bacteria are trapped in the filter. It is possible to separate toxic arsenic, ions, salts etc. from water.

Algae like Nostoc, Anabaena, Aulosira etc. have heterocysts. Heterocysts fix nitrogen. These algae convert nitrogen into usable ammonia.

Different types of algae are used as fish food. So algae are used in ponds or reservoirs for fish farming. Several types of algae are used as feed in tilapia fish farming.