What safely kills algae without harming fish?
Written by
Wang Jiahao
Reviewed by
Prof. Henry Webster, Ph.D.Fish tank owners frequently inquire about what reduces algae that is safe for their pets. The answer can be a variety of things that help kill algae while being safe for fish and other aquatic life. Physical removal of algae can provide immediate results and requires no chemicals. Biological controls can be natural methods that kill algae. A UV sterilizer is a high-tech means for "killing" algae. Whatever method you choose, don't forget to treat the original cause of the algae growth, such as excess nutrients.
Manual Techniques
- Scraping: Use plastic blades on glass or acrylic-safe scrubbers
- Vacuuming: Remove algae during water changes with gravel vacuums
- Brushing: Clean decorations with soft-bristled brushes in tank water
- Filter cleaning: Rinse media in removed tank water to preserve bacteria
Biological Controls
- Amano shrimp: 1 per 2 gallons for thread algae
- Nerite snails: Effective against glass spot algae
- Otocinclus: Groups of 6+ consume soft algae films
- Siamese algae eaters: Need 30+ gallon tanks for BBA control
UV sterilizers safely eliminate free-floating algae. Carry it after mechanical filtration in the system. Use at least 10 watts per 50 gallons of water. It kills algae cells floating in the water but does not affect beneficial bacteria attaching to the surface. For spot treatment of algae, use hydrogen peroxide. Apply a maximum concentration of 1 mL per gallon directly to algae patches.
Preventing future algae problems can be easily done by controlling nutrients- Cut down on feeding so fish eat what they can in about two minutes; make regular water changes; use media in your filter designed to remove phosphates; balance your duration of light; these things, whilst making the fish happy, will make algae unhappy.
Monitor your tank closely after treatment. Test your water parameters weekly. Observe the behavior of your fish. You should see a reduced regrowth of algae in your home aquarium. A successful algae control means a balance of the ecosystem. Your fish will be actively swimming about at normal levels of feed and fish keeping. Your plants will thrive as well. This indicates that you have a truly algae-managed environment.
Read the full article: Comprehensive Fish Tank Algae Control Guide
