A cloudy fish tank can be alarming but the problem can be easily dealt with when you know what you are doing.
If your aquarium water is cloudy, foamy or smelly then you need to take action to wash and clean it because if it is in this condition it will almost certainly bring about stress and disease to your fishes.

Clear Fish Tank
The problem of a cloudy aquarium is caused by a high concentration of algae and bad bacteria in the water. This bacterium feeds on light, excess fish waste and uneaten fish food that builds up eventually to high levels of nitrates substrate that if left unchecked will probably cause stress and disease to your fish.
The first action you need to take is to find out how to clean a fish tank correctly so you can clean out algae growth, excess nitrates and bad bacteria from your aquarium water.
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As a quick fix you should set about cleaning and changing the water but not all in one go as this will be very damaging to your fishes. Aim to improve and change, around 10% to 20% each day, until in time it is completely replaced. As you replace a percentage of the water, you'll be removing some of the cloudiness caused by dissolved food and waste. This will then begin to remove the food source of the bacterium bloom. Once the aquarium is clear you can go back to changing a percentage of the water twice a week instead of every day and then weekly.
Reduce Cloud In Your Aquarium By Reducing the Amount of Food.
People giving too much food to their fishy friends often causes a cloudy fish tank, so reduce the amount of food you give to them. A way to ensure they eat all the food that you feed them is to remove any uneaten food after about 10 minutes. One of the biggest mistakes new fish keepers make is to over feed their pets and not clean the debris and decaying material away.
Reduce Opaqueness In Your Aquarium With Good Gravel.
Opaque aquarium water can be helped greatly by introducing cultured gravel from an established aquarium with healthy fish to the bottom. Simply sprinkle the good gravel on top of the gravel that you already have in your tank. The beneficial bacterium that is living on the good gravel will quickly multiply to cover the surfaces of the rest of the gravel in your cloudy aquarium. The beneficial bacterial will digest the waste in your water, and the water will quickly clear.
Always Have Good Water In Your Aquarium.
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Cloudy aquarium water can be caused by a high level of dissolved compounds such as heavy metals, phosphates, nitrates, substrate or silicates. If you think this could be the cause you should test the water and if there is a problem you can treat your cloudy fish tank water with conditioners that should resolve the problem. If it doesn’t then you may need to use RO or Reverse Osmosis water.
Reduce Problems With Good Maintenance.
Proper tank maintenance will stop any occurrence of algae and problem aquariums but if it doesn’t then you need to make sure the aquatic filtration system is able to handle the size of tank you have and the number of fishes you're keeping.
Don’t be too alarmed by cloudy fish tank water because if you take the right steps you will soon eliminate the problem in your cloudy aquarium.
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