Cloudy water after water change


Aug 9, 2021
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For a number of years, I have never had anything but crystal clear water after changes. This tank is less than 6 months old, but the same has applied since owning it. That is until the last 2 water changes. Both times, I have noticed the water go cloudy within hours of changing the water. By the next day it is crystal clear again. I’m not concerned, more confused as to what would cause this. I have not changed a single thing surrounding water changes and maintenance. Parameters are spot on, fish are fine, just confused how I’ve done the same thing for 5 months on this tank, and now all of a sudden it is cloudy every time? Pics of before and after water change.


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Looks like a microbial bloom. A new tank's ecosystem is still establishing its balance of beneficial bacteria that break down waste. Even a small water change can disrupt this balance and cause a temporary spike in free-floating bacteria, making the water cloudy. This is especially common in tanks under 6 months old, which aligns with your timeframe.

The good news is this cloudiness is usually harmless and clears up on its own within a day or two, just like you've been experiencing. If this is the case, there's no need to be worried. The tank will naturally re-establish its bacterial equilibrium. And sooner than later all should bounce back to normal when you do water changes.
The first time I cycled a tank the bloom last 10-14 days and then cleared.
Hello. A water change will stir up small particles that can make the water hazy. After a few hours, the filter will generally clear up the water. Some time ago, I learned that by installing a temporary second filter, you can get clearer water faster, so I always had a spare filter with all the media for that purpose. Now, I'm not so concerned about hazy water. As long as I know the water is clean, I'm happy.

It's just a bacterial bloom. Harmless. The way it was explained to me is this. These are different bacteria than the beneficial bacteria of the nitrogen cycle. These bacteria feed on carbon or something like that. When we dechlorinate the water, that allows them to proliferate. But then their population crashes and the water clears up. Everyone sees this when they start a tank. I still see it sometimes after a large water change. It always clears right up.
Do you clean the filter or the filter media at the same time as the water change? What method do you use?

Do you add any chemicals or additives at the same time as doing a water change? At what dosage?

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