Why Is My Aquarium Water Cloudy?

White or gray cloudiness in a new tank is often a bacterial bloom. It looks alarming but usually fades within one to two weeks as the filter and cycle mature. Resist the urge to scrub everything or change 90% of the water — that can reset progress. Keep feeding light if fish are already in, and test ammonia and nitrite.

Green water is typically free-floating algae, often tied to too much light, too much nitrate, or overfeeding. Cut the photoperiod to eight or ten hours, reduce feeding, and keep up with partial water changes. Brown or tea-colored water may be tannins from driftwood or peat — harmless for many setups unless pH drops more than you want.

If cloudiness returns after the tank was clear for months, check for a dead fish, clogged filter, or recent overfeeding. Log parameters when it starts so you have a before-and-after record in ReefDiary.