Why Is My Fish Tank Cloudy?

Is the cloudy aquarium water green?

Is your aquarium placed in a spot with lots of light?

Do you feed your fishes excessively or is the water source rich in phosphates?

Was the water cloudy immediately or within an hour or two of filling the tank?

Did the cloudiness appear days, weeks, or even months after the filling of the tank?

Placing the aquarium in direct sunlight or leaving the lights on too long will result in algae growth. Reduce the amount of time the lights are on, and move the aquarium to a location out of direct sunlight.

Phosphates encourage algae growth. Phosphates come from two sources—decaying matter such as fish food, and from the water source itself. Testing your tap water for phosphates will let you know if you have a problem with your water source. If your water naturally has a high level of phosphate, you will need to use RO (Reverse Osmosis) water or a phosphate remover to treat the water. Reducing the amount of food you give your fish, and changing to a brand that is lower in.

Nitrates encourage algae growth. Nitrates naturally rise in the aquarium over time as a byproduct of fish wastes. The only way to remove them is to perform a water change. Make sure your filter is kept clean and is adequate for your tank size. Also, make sure you have not overstocked your aquarium, or you will constantly battle rising nitrate levels.

If the water is cloudy immediately or within an hour or two of filling the tank, it's probably due to insufficiently washed gravel. Drain the tank and rinse the gravel until the water runs clear. That should resolve the problem.

The cause for this is usually due to bacterial bloom. As the new aquarium goes through the initial break-in cycle, it is not unusual for the water to become cloudy or at least a little hazy. It will take several weeks to several months to establish bacterial colonies that can clear waste from the water. Over time, that cloudiness will resolve itself. Decaying plants or excess food that remains uneaten can also cause the milky water seen in bacterial bloom.

Often cause of cloudy water in a fish tank is a high level of dissolved constituents, such as phosphates, silicates, or heavy metals. If you test the water, you'll likely find that the pH is high (alkaline). In these cases, treating the water with conditioners will often resolve the problem. Another option, which has many benefits beyond resolving cloudy water, is to use RO (Reverse Osmosis) water. Your local fish shop may sell it or sell units capable of making RO water.