Cloudy water is a description, not a diagnosis. Its colour, timing, and the change that came immediately before it usually reveal the useful next step.
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A white or gray haze in a new aquarium is often a bacterial bloom while the microbial community settles. It can look dramatic and still clear on its own. Test ammonia and nitrite during the bloom because appearance cannot tell you whether the water is safe.
Green water comes from free-floating algae and points toward available light and nutrients. Brown or tea-coloured water may be tannins released by wood or leaves. Fine substrate can also create a dusty cloud after planting or maintenance, especially if it was recently disturbed.
Work backward before buying a cure. Ask whether the tank was just started, the filter was deep-cleaned, feeding increased, substrate or wood was added, or several fish arrived. The timing often identifies the cause more reliably than the colour alone.
Avoid tearing down the aquarium or replacing all filter media in response to a haze. That can remove established biological capacity and create a larger problem. Preserve mature media, correct the identified source, and use partial water changes when testing or livestock condition supports them.
Bottled bacteria may be relevant when establishing or rebuilding biological filtration, and an additional sponge filter can add biological and mechanical capacity. Neither product is a guaranteed cloudy-water cure because neither addresses every possible cause.
Treat gasping, lethargy, or measurable ammonia and nitrite as urgent. Otherwise, document the change, keep testing, and give an ordinary bacterial bloom time to settle instead of stacking several interventions at once. Clear photographs taken under the same lighting can also show whether visibility is improving from day to day without relying on memory alone.
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