Why Has My Tank Gone Cloudy?

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Cloudy water can have a number of causes but the most common, a bacterial bloom, is also the most serious and is to do with water quality and the bacteria in your filter.

Bacterial blooms often occur in new aquariums and the cloudy water is caused by a rapid increase in bacteria as a result of an increase in waste product. Until bacteria settle at a steady population in the filter, they can fluctuate rapidly in response to fluctuating water conditions.

In a new tank without fish, this process is not harmful and should clear within a few days before fish are added. If a bloom occurs in a new aquarium after fish have been introduced it would be wise to check water conditions, particularly ammonia and nitrites, but it may also just clear in a few days.

In well-established tanks a bacterial bloom will only occur when the waste processing system has been disrupted somehow. This could happen if the filter is switched off for a long period, if media is cleaned in tap water, or if all the filter media is replaced, all of which will cause a loss of filter bacteria followed by a sudden increase of pollutants and a bacterial bloom.

In these cases it is vital to keep a close eye on water conditions and regulate your feeding levels, reducing or even stopping feeding if there is ammonia or nitrite present in the water. The addition of a live bacteria product will help to re-establish filter bacteria.

Cloudy water can also be caused by an algal bloom, although the water will normally appear green, or it can simply be a build-up of waste particles. If the water has steadily got cloudy over a longer period and you can see particles floating around in otherwise clear water, it is simply a particle problem and can be cleared up by improving filtration.

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