Will this cloudy water clear?


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A reader is concerned about cloudy water in his new tank set up.

I set up my new 200 l tank at 4pm in the afternoon, and when I went to bed at 10pm that evening, the water was clear. However, by the morning the water had turned cloudy. I carried out a 50% water change but it has still remained cloudy. The tank is filtered by a 1200IF All Pond Solutions internal filter and I have added a bacterial starter. The pH is 7 and there have been no ammonia warnings. What can I do to remedy the cloudy water situation?


Bob responds: Cloudy water is a relatively common problem in recently set up aquariums, but it’s generally nothing to worry about. You don’t mention the type of substrate you have chosen but some of these, especially the clay-based growing medias, can cause some cloudiness, particularly if you have vigorous water movement. But, if your tank was clear when you left it for the night, and then cloudy by the next morning, it seems likely that the cloudiness is the result of a bacterial bloom. These are a harmless side effect of the first stages of a tank establishing itself biologically and usually clear themselves in a few days. 

A bacterial starter helps with cycling the filter and establishing beneficial bacteria in advance of adding the first fish, and it should also help with the clarification of the water. If possible, I would recommend adding a source of ammonia to the tank (if you don’t already have livestock present) to help further advance the cycling in preparation for the addition of your first fish.

Don’t carry out any more water changes for the next couple of weeks, as this can actually slow the process of maturation, but do keep a close eye on the water chemistry and consider water changes if the pH drops rapidly.