What To Do About Cloudy Tanks

By Sue McGregor

As a pet store owner, I am frequently asked questions by local hobbyists regarding the upkeep of their aquariums and care of the fish within. Some questions come up repeatedly, so I thought it might be beneficial to address some of these problems here, besides, I was tired of feeling guilty whenever the editors asked for (pleaded for) submissions from the members...

The question I've heard most often lately is, "Why is my tank cloudy?" The frequency of this inquiry coincides with a rash of new tanks, set up following the Christmas holiday! While most experienced hobbyists are familiar with what's going on, I decided that this was a good topic to begin with, since it discourages many beginning aquarists.

There are several different reasons for a cloudy appearance in a tank, but when it occurs in a new tank it may be one of several symptoms of "New Tank Syndrome". Sometime between one week and one month after a tank is set up, the water may appear "cloudy". Exactly when this happens, and to what degree, depends on when and how heavily the tank is stocked. Water cloudiness is, unfortunately, a normal part of a tank's establishing itself.

So what exactly is "it"? It is a bacterial bloom. Are the bacteria harmful to fish? By themselves, probably not, but they may be associated with high levels of ammonia and nitrites in a new tank, both of which are very harmful to fish. In this case, it's important to do frequent partial water changes to keep these levels as low as possible. How do I get rid of the cloudiness? There are a number of things that may help. Your eventual goal is to establish a colony of "good" bacteria, which will utilize and break down the bacteria clouding the water. "Good" bacteria also turn ammonia and nitrites (which arise from fish wastes and decayed food) into nitrates (which are relatively harmless to fish in low concentrations). So where do you find some of these desirable bacteria? They are found in established tanks on every surface: on the gravel, on the glass, in the filters, in the water, even on the fish. Probably the easiest and most recommended way to introduce some of these good bacteria into your tank is by putting some hardy fish into your tank. This may not be the fastest way, however, and stocking too many fish will pollute the tank faster than the bacteria can grow. That's why reputable pet shop personnel encourage new tank owners to "go slow" at first. Other ways of introducing beneficial bacteria into your tank are: take a handful of gravel from an established tank; fill your tank with water from an established tank; use a filter cartridge from an established tank. There are also several good products you can buy that will aid in the establishment of bacteria, when added to a new tank. When bacteria are added to a tank they sometimes seem to take off suddenly. The tank may clear overnight. One customer of mine had been battling a cloudy tank for weeks. In desperation, she asked me for advice. I gave her a couple of handfuls of gravel from one of our shop tanks; the next morning, her tank was crystal clear. She swears I performed magic!

If your tank doesn't clear up overnight, you can somewhat alleviate the problem by performing frequent partial water changes (as often as a couple of times a week, 10 to 20%, taking care not to disturb the gravel too much if you have an undergravel filter, as this is where the majority of your bacteria are building up), and limiting feeding for several days. Don't add new fish while the tank is cloudy, and try one or more of the methods suggested above for adding more bacteria to the tank. For a quick fix, you might try running a diatom filter on the tank for a short while; however, the cloudiness may soon return if the "good" bacteria are still not present.

What about when cloudiness occurs in an established tank? Probable causes include overfeeding, insufficient filtration, or the growth of algae in the water. Solutions for the first two are obvious; the growth of algae is a subject deserving of an entire column in itself!

If you are battling cloudy water in a new tank, be patient! Remember, it's a normal phase your tank may go through, but if you are diligent in performing regular partial water changes and don't overstock your tank, you will soon be rewarded with clear, sparkling water and happy, healthy fish!