Cloudy Water, Still Fish: Surviving Your Tank's First Month

Your brand new tank goes milky on day four and the fish are sitting on the gravel like they've given up. It's the most common thing that happens to new aquariums — and it's almost never dirt. 🐟

That haze is a bloom of bacteria multiplying in water suddenly full of ammonia. The same ammonia is burning your fish's gills, which is why they're sunk at the bottom breathing fast. The cloud is a symptom, not the problem.

So don't reach for the clarifier and don't scrub the filter — those bacteria are the cure. Get a liquid test kit, change 25–50% of the water with dechlorinated, temperature-matched water whenever ammonia or nitrite reads above zero, feed very lightly, and add an airstone.

A filter takes two to six weeks to mature. Patience really is doing something here. Our full guide covers what each colour of cloudy water means, a step-by-step first 48 hours, and the signs that need a fish-savvy vet.