Algae, autotrophic organisms with plantlike characteristics (including carrying out photosynthesis), mainly grow in aquatic environments. Algae—especially green algae—can often show up in your water bottle—especially when you are hiking or doing another outdoor activity. You can safely clean algae out of a water bottle in 3 main ways.
Bleach, an effective overall disinfectant, will certainly remove the algae completely. Fill the dirty bottle with 1 part bleach, 1 part water. Allow the mixture to sit in the bottle for 12 hours. Rinse out the bottle completely to avoid ingesting any bleach residue.
A lesser-known means for removing algae, 3 percent hydrogen peroxide can also clean your bottle without requiring any scrubbing. This time, use 1 part peroxide and 2 parts water. Once you've filled the bottle, allow it to sit overnight. The bottle should contain no trace of algae after this.
For a less toxic method of cleaning algae, try using vinegar. Use equal parts vinegar and water and a brush to scrub the algae out of the bottle. Rinse out the bottle well.
Algae can have toxic properties. If for any reason, you cannot completely rid the bottle of the algae, buy a new bottle to avoid getting sick.