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Why Is My Water Cloudy?

Maintaining a Clear and Attractive Aquarium

(The First Tank Guide)

Many people have problems with water clarity in their aquariums at one time or another. There are several factors that influence water clarity in an aquarium. Some of these are related to the age of the tank, others are related to the care and maintenance provided, and still others are related to outside influences.

Water Clarifiers

Though there are quite a few chemicals available on the market to help clarify your aquarium water, these are really only going to hide a symptom that should be addressed by providing proper care to the tank to keep the water clear.

In my experience, these chemicals will only clear the water up under circumstances where the water would have cleared itself up in a few hours, and otherwise have little or no effect. In fact, some people who have had perpetual problems with cloudy aquarium water and have been using these chemicals get their aquarium to clear up within a water change or two after they stop using the water clarifier! This makes it look like the aquarium water clarifier was causing, or at least contributing to the cloudiness or milkiness in the water.

Cloudy Water in New Aquariums

When you first set up your tank, your tank has to cycle so the biological elements of the filter are ready to handle the waste produced by the fish. Cloudy or milky water is common during this process, but it usually does not show up until fairly late in the cycle.

If your tank has only had fish in it for a couple of weeks, or if it is new and has had a lot of fish in it for a few days, then this is the most likely cause of the cloudiness you are experiencing.

Unfortunately, the only way to get rid of this cloudiness is to have patience. As the cycle runs its course, this cloudiness will clear up—usually your tank will go from cloudy to nearly crystal clear overnight—as soon as it is ready.

During this time, remember to continue your extra water changes (about 10-15% twice a week while the tank cycles), and to be very careful about feeding your fish. Adding chemicals to try to clarify the water in a tank that is still cycling will often hamper the cycling process, and is unlikely to have much effect on the cloudiness.

Cloudy Water and I Don't Have Fish Yet!

If the tank is very new, and you don't yet have any fish (so the tank has not yet started to cycle), then a white or gray cloudiness is likely due to some piece of decoration or equipment not being thoroughly rinsed with cool running tap water prior to introducing it to the tank.

If you have any equipment that was not thoroughly rinsed before you put it in the tank, then you have probably found your culprit. If this is the case, then the mechanical elements of your filter should remove the suspended debris that is causing the cloudiness. If the filter does not remove it, then it will be removed by your regular water changes.

It is possible that some item that is being used as a decoration in the aquarium is dissolving in the water or is otherwise not aquarium safe. This can produce any color of cloudiness, though gray or milky-white is most common. This object should be removed, and a large water change should be done.

Check the tank for any decorations that were not sold as aquarium decorations from a reputable pet store. Be sure to thoroughly check any rocks that have been put in the water to see if any of them have changed shape like they are melting, or if any section of one has become soft or loose. If you find any soft spots or any change in shape, you should remove this item from the water.

Also check for decorations that may have paint flaking off or other discoloration or damage. Additionally, unless the tank is saltwater, brackish water, or a Rift Lake environment for African Cichlids, you should remove any real coral skeletons or sea shells that are in the tank, as these can contribute to elevated pH and hardness.

After removing a problem decoration from a tank, the cloudiness should go away with a few water changes and your regular filtration.

My Fish Tank Water Is Cloudy and It Has Only Been Up for a Few Hours!

If your tank has only been set up for hours (or sometimes even minutes) and you are seeing a grayish cloudiness, it is possible that this cloudiness is due to tiny bubbles of air suspended in the water. This will usually look silvery or white, more than grey; and is usually bright and reflective, rather than dull and dark.

This cloudiness should dissipate over another few hours as these air bubbles dissolve into the water or rise to the surface. This type of cloudiness can also happen after large water changes.

My Aquarium Water Looks Like Weak Tea, It's Not Milky

Wooden decorations produce a perfectly safe form of cloudiness by releasing tannin into the water. The tannin will give the water a yellowish or brownish cast, somewhat like very weak tea. However, these are helpful in softening the water, lowering the pH, boosting many fishes' immune systems, and often improving the coloration of your fish. Some studies show that this will increase fish's appetite, reduce stress, and even stimulate spawning. I have seen the addition of a wooden decoration to the tank stimulate spawning behavior in some soft-water catfish or tetras that spawn with the spring floods, so this does seem to have some credibility.

My Fish Tank Is Green!

Green aquarium water is usually a free-floating algae bloom. Though many of the tips for controlling algae growth in your fish tank are the same as for other forms of cloudiness, specific tips on algae control may be more helpful.

What Else Causes Aquarium Cloudiness?

Chemicals that have been added to the tank could react with other chemicals in the tank (or even something in your water) and create a variety of forms of cloudiness. This cloudiness can be prevented by minimizing the use of chemical additives in the tank. Also, testing with small amounts of chemicals in water containers may give you an idea of what could be reacting. In many cases, this cloudiness will be corrected quickly by the chemical elements of your filter, and, of course, by your regular water changes.

Insufficient water changes can be a cause of cloudiness, as assorted debris collects in the water or the remnants of fish waste and uneaten fish food begin to float through the water. Insufficient water changes can also lead to algae or bacteria blooms that will make the water appear cloudy. You should perform a weekly 10-15% water change in your aquarium, though you will need to increase the frequency of these water changes if the tank is still cycling. Oddly enough, excessive water changes can also cause cloudiness, as removing too much water from the tank will disturb the bacteria bed that is providing your biological filtration, and your tank may become cloudy for a few days as the biological filter reestablishes itself. Regular, frequent, small water changes will help to keep your aquarium clean, clean, and healthy.

Over feeding, can also cause cloudiness in tanks that have been set up longer. Remember to feed sparingly. Your fish's stomachs are usually smaller than their eyes, and they should be able to completely consume all the food they need in under two minutes.

Overpopulation can also be a a cause of cloudiness in an aquarium. Too many fish in a tank leads to stress, shortened lives, additional maintenance, algae growth, and cloudy water. Keeping your tank's population at or below 1" of fish per gallon of water for small community fresh water fish will keep this cloudiness under control.

If your tank is insufficiently filtered, or if your filter is not maintained properly, then the filter will not be able to efficiently process all the water in the tank, which, like insufficient water changes, can lead to cloudiness directly, or to algae or bacteria blooms that appear cloudy.

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