The milky white cloudy water you are seeing is called a “bacterial bloom”. Let me explain what is happening and how to fix it.
After setting up a new aquarium and filter, we put in fish. The fish begin to immediately excrete waste into the water in the form of ammonia. This ammonia is toxic to the fish and so we want to get it out of the aquarium, which is why we use a filter, a biological filter.
The way a biological filter works, is by growing live beneficial bacteria that actually eats the ammonia in the water and converts it to another compound that is not toxic to the fish. These special live bacteria need food (ammonia) to multiply and grow and a place to settle down in the filter. The media in the aquarium filter becomes the surface area for the bacteria to settle on and live while they consume ammonia.
New aquariums and filters are sterile and do not have many live bacteria to start. As ammonia excreting fish are introduced, the bacteria begin to multiply by the billions in order to handle the ammonia level in the aquarium making it look white and hazy, thus a bacterial bloom.
Once enough special live bacteria have multiplied and inhabit the media areas in the filter, the rest will die off and the aquarium water will get crystal clear. If you do a water change during this process of establishing the baseline bacteria it is like starting the aquarium all over again and you will continue to get cloudy, hazy water. The best thing to do in a new aquarium that is cloudy is to leave it alone as it will clear up on it’s own once enough bacteria have formed usually within the week.
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