Why is my aquarium water cloudy?

White or grey cloudy water

Often a bacterial bloom in new tanks during cycling. It usually clears as the cycle establishes. Do not over-clean the filter. Grey can be dust from new substrate or stirred debris.

Green cloudy water

Usually a free-floating algae bloom. Reduce light hours, do partial water changes, and cut back on feeding. See our green water guide.

Quick takeaways

• White or milky often means bacterial bloom in new tanks; usually clears with the cycle.
• Green means algae bloom; reduce light and nutrients.
• Do not over-clean the filter or overdose clarifiers.