Green Algae in Your Delhi Water Tank? How to Fix It

Green or blue-green tint on the walls, slippery surfaces, and a musty smell — that is algae, and in Delhi it is overwhelmingly a summer problem with a simple root cause.

Why your tank has it and your neighbour’s does not

Algae needs three things: light, warmth and standing water. Delhi supplies the warmth for eight months a year and your usage pattern supplies the standing water. The variable is light — and that is almost always the tank itself.

• Translucent white or light-coloured plastic tanks pass enough light to grow algae
• A cracked, warped or missing lid lets light in directly
• Tanks in unshaded direct sun run hot and grow algae faster
• Dark, opaque tanks in shade rarely have this problem at all

Fixing it properly

Algae grows into biofilm, and biofilm bonds to the wall. Wiping it leaves the anchoring layer intact, which is why it is back within three weeks. The tank needs draining, sludge extraction, high-pressure jetting of every wall and corner, and disinfection with adequate contact time.

Stopping it coming back

• Block the light. The single most effective fix. An opaque tank cover, a shade structure, or replacing a translucent tank with a dark opaque one
• Seal the lid. A properly seated lid with an intact gasket blocks light and insects together
• Mesh the overflow. Cheap, quick, and closes the second entry route
• Do not let water stand. Tanks on long holidays should be drained, not left half full and warm
• Clean quarterly in summer. Half-yearly is enough for winter; it is not enough for a Delhi May

Is algae dangerous?

Most tank algae is a nuisance rather than a toxin — it affects taste, smell and appearance. But an algae-friendly tank is also a bacteria-friendly tank, because both thrive in the same warm, lit, stagnant conditions. Treat visible algae as a signal about the whole environment, not as a cosmetic issue.