There are a couple of things that could cause white cloudy aquarium water. The good news is that they are easy to treat once you narrow down the cause. Dirty substrate or decorations, or a bacteria bloom are the usual suspects.
Dirty Substrate or Decorations
This is very common reason for cloudy aquarium water in newly set up fish tanks. It is important to thoroughly rinse your aquarium substrate and decorations before putting them in your tank. If you believe this is the reason for your cloudy fish tank water, there are a couple of things you can do. Give it a couple of days and you should notice that the particles fall to your fish tanks floor leaving clean water behind. If this doesn’t happen on its own you should start 20% water changes until your water clears.
Is a Bacteria Bloom the reason For My Cloudy Aquarium Water?
Did you just do a large water change? Have you just thoroughly cleaned your tank? Have you just medicated you fish? Have you just set up your tank? All of these things can sometimes cause a bacteria bloom. If this sounds your situation, you the best advice is to sit back and wait. When those bacteria establish themselves, your cloudy aquarium water should clear up on its own.
Just Give it Some Time
As you may have noticed the basic treatment for white cloudy aquarium water is to hurry up and wait. There are chemicals available but they are not recommended. White cloudy aquarium water will almost always clear up on its own.