Algae Control in Water Tanks
Why algae grows in stored water, how opaque and black tanks suppress it by blocking light, and the potable-water considerations (NSF/ANSI 61, treatment, screened vents) that keep stored water fresh.
Algae needs two things to grow in a water tank: light and nutrients. Take away the light and it cannot photosynthesize, which is the single most reliable way to keep stored water from turning green. Algae is a plant, and in untreated water exposed to direct sunlight it can begin growing within about 72 hours.
Why Translucent Tanks Go Green
A white or natural-colored plastic tank lets light pass through the wall. That is exactly the condition algae wants, so a translucent tank sitting in the sun is close to an ideal place for it to bloom. Beyond looking bad, algae is hard on the human digestive system and fouls filters, fittings, and pumps downstream.
How Opaque and Black Tanks Suppress It
- Black or dark opaque tanks block the sun's rays from reaching the water. No light through the wall means no photosynthesis, and algae growth is stopped at the source. This is why dark and black tanks are the standard recommendation wherever a tank sits outdoors in daylight.
- Move white tanks indoors if a dark tank is not an option. Indoors, algae grows far more slowly. It can still grow in a white tank under artificial light, just at a reduced rate, so an opaque tank is still the better answer.
- Keep the tank sealed with screened, covered vents. Cutting off airborne debris and spores, on top of cutting off light, keeps stored water cleaner for longer.
Treatment as a Backup
Treating the water with a small amount of chlorine will also keep algae from growing. It works, though it adds a bit of a taste to the water. For most outdoor storage, an opaque or black tank is the simpler fix because it removes the light instead of chasing the growth chemically.
Potable-Water Considerations
If the water is for drinking, algae control and material safety go together. Use a tank certified to NSF/ANSI 61, the standard for drinking-water system components, and pair the opaque tank with appropriate treatment for potable use — a sediment filter, activated-carbon filter, and UV disinfection are common. Opaque construction is also a core requirement for rainwater harvesting storage for the same reason: keep the light out, keep the algae down.
What Tank Systems Offers
Tank Systems supplies black and dark-colored vertical tanks built to keep stored water fresh, along with the vents, screens, and fittings that go with them. Tell us the volume, whether the water is potable, and whether the tank sits indoors or out, and we will point you to the right configuration. Contact us or request a quote for a water-storage tank sized to your application.
Need Technical Assistance?
Our team is ready to help with material selection, system design, and specifications.