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Why does my aquarium look like someone poured milk into it?

Updated on March 19, 2009

New Tank Syndrome - It happens to the best of us!

New aquariums start with sterile water, the water company often treats with anti bacterial compounds that are there to kill any bacteria or other pathogenic organisms that might cause a human to become ill. Once used, they make the water "potable". Potable water may be deadly to bacteria, but it is kills tropical fish as well.

Your municipal water supply uses chlorine (in most cases) and/or chloramine - when the water needs to be transported a great distance. Although the two compounds require different doses of the same neutralizer, once they are removed, the water is left virtually with no living organisms. But there is always the ability to support them when they do.

The first life to arrive are usually single celled bacteria suspended by the water. These are very rapid regenerating bacteria that simply split in two to replicate. The fast multiplication of bacterial population is called geometric replication. The process allows one to become two, two become four, four double to eight and so on. Each generation roughly doubles in size. Since the water begins by being sterile, there are reasons for the this huge population bomb to slow down.

What occurs in the brand new rank situation is described as the phenomenon of "New Tank Syndrome". It normally takes about three days to develop after the water is placed in the aquarium and the chlorine/chloramine is removed. Cloudy water is actually quite common. It is not very dangerous to fish, but it is not pretty.

The only real problem is the bacterial cloud consumes oxygen, which could become a problem in an overstocked aquarium, which a new aquarium certainly should not be! You might want to elevate the oxygen content with an added airstone bubbling air to agitate the surface during a cloud. If the fish seem to be gasping, adding an airstone to agitate the surface may alleviate the problem temporarily.

The only limiting factor to this unchecked population growth is the amount of nutrients available. The tapwater includes much more than just water and chlorine, it often contains a lot of dissolved organic material as well. This provides the nutrition required by the bacteria. When the nutrients are plentiful the bacterial population elevates to abnormally high levels. It takes about three days for heterotrophic bacteria to become so dense that the bacterial bloom can actually be detected by the unaided eye. It appears that someone poured a glass of milk into the tank. Depending on the amount of nutrients dissolved in the water and there for the bacteria, this can become quite dense and very murky white in appearance. Unchecked bacterial growth in the water is called a bacterial bloom.

This is quite a common problem for many new aquariums, especially when new water carries with it considerable amounts of dissolved nutrients. In northern climates when there is a spring run-off, the amounts of dissolved compounds in the water from the tap rises dramatically. Many new tanks show this problem in the spring when the water from the tap is at its worst.

The nutrient density in the water is also the limiting factor. Once the food is used up by the huge population of bacterial strains, there will be mass starvation. That sudden loss of bacteria may take some time if there is additional food being added on an ongoing basis. This elongated life of a bacterial cloud can occur from the feeding practices of the aquarist. Too much overfeeding and the the problem becomes perpetual.

"New Tank Syndrome" can occur with or without fish. And it is not the fault of a common filter, the bacteria are much too small to be captured by any ordinary filter. If a newly set-up tank clouds before you add fish, simply do nothing. The cloud should dissipate on its own.

If the bacterial bloom occurs when fish have already been added to the beginning aquarium, it is best to allow nature to take its course, Refrain from feeding for about three days to allow the bacteria in the water to eat until they finally starve. Don't add more food, or the problem may become chronic. If you must feed, feed only once a day and ensure that the fish eat everything offered in two minutes with nothing hitting the bottom. A little nutrition may be fine, but do not overfeed even a slight bit.

A bacterial bloom can also occur much later in the aquarium's life cycle. In these cases, it is most often due to overfeeding or excess waste accumulating in the tank. This is a case where the nutrients from waste materials rise to a level where they stop being a limiting factor. When this happens, a bacterial bloom goes out of control.

The most basic cure is to reduce the amount of organic material wastes in the aquarium. Remember, the aquarist is ultimately responsible for what enters the aquarium. The cure is to reduce the input. During feeding and maintenance, examine the fish tank's bottom for dead fish or decaying material. Perform regular water changes. Use the removing water to drive a gravel cleaner through the substrate. This helps ensure the heaviest source of debris is removed from the aquarium.

Once the aquarium water removal and replacement has reduced the wastes and the tank is back into a healthier and hygienic shape, stop feedng the aquarium for at least three days. Chances are the original cause was overfeeding. By fasting the fish, they must go looking for a meal rather than simply patroling for one at the surface. Fish look harder for even small tidbits when they are hungry. This even helps clean the tank a bit and can greatly improve the overall environment.

As the three days pass, the bacteria catch up to the organic overload, and the critical period comes where they are starved back from lack of food. Hopefully they soon die back again to invisible. Once the three day fast is over, resume feeding. But since it was overfeeding that normally got the aquarium into the problem in the first place, feed less and less often to keep wastes to a minimum.

A bacterial cloud is rarely a filter's fault. The bacteria are much too small to be trapped by the filter media in most cases. The only way to help the filter capture this small an organism is to add a product that clumps them together. There are clarifier products that do just this. They ionically force the bacteria along with most other supended particles to coagulate into large enough clumps that they can be trapped by the filter.

The result is a gooey mess that is quite difficult to remove. Whenever you decide to use a floculant - the technical term for a product that clumps all particles together - you should not remove it with standard filter materials. The best replacement media available is Poly Wool. It can also be called Filter Floss or Angel Hair. This classic box filter media consists of very fine threads and is quite cheap. Purchase it knowing it is to be used for a few hours and then thrown away once it has been used. It traps clumps quite readily. Once the gooey mess is removed from the filter chamber, it is easy to dispose. Don't use expensive standard media or cartridges. Once they have been exposed to the floculant you are simply going to have to discard them immediately.

One final word of warning, if you use a floculant, dose for the exact amount of water in your tank - remember that heavily decorated aquariums have quite a bit of volume used by rocks and such which can quite measurably reduce the actual water capacity of the aquarium. Be very careful in your doses. This is one product where more is definitely not better.

An overdose reverses the ionic attraction effect. The water may become even more cloudy and difficult to clear if an overdose should occur. Account for the loss of water volume by decorations and gravel when measuring the treatment. Consider it a one time thing. It should not become something you can depend on regularly.

Reduce the food entering the aquarium. Ensure anything that dies is removed as fast as possible. Cleanliness, for the most part in an older aquarium will help keep the tank clear and cloudless. Refraining from adding too much food and organic material to the aquarium is better than any medication or chemical treatment.


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    • Cris A profile image

      Cris A 

      9 years ago from Manila, Philippines

      You just answered an age-old question right there. So it is actually a syndrome and has a name, too! Hobbyists should read this very informative hub. Thanks for sharing :D


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