Unfortunately, aquariums sometimes have a will of their own, and too often an aquarist will come home to find the water in their aquarium displaying unusual colors. That is a sign that something has gone wrong - but what?

The color of aquarium water can tell a lot about what is happening inside the tank, and more often than not, getting back to that perfect, clear tank is not always difficult once you correctly diagnose the problem. No matter what the tank is doing, water chemistry tests and small water changes should be done regularly.

The first discoloration a new aquarist is likely to see is a cloudy, hazy, or white aquarium - sometimes appearing with no warning overnight. This is appropriately known in the hobby as “New Tank Syndrome” (NTS) since it happens most often within the first few weeks that a tank is up and running. NTS is caused by an overpopulation of bacteria. That bacteria is absent in a pristine aquarium, so when introduced it can explode in population to fill the available space,overpopulate, and ultimately die off. The cloudiness is itself harmless, but it almost universally accompanied by dangerously high ammonia levels. Despite the name, New Tank Syndrome can happen in established tanks, too, if the bacteria population is disturbed or the ammonia levels spike suddenly (such as when new fish are introduced).

In a new tank with no fish, the best solution is: do nothing. Most of the time it will resolve itself within a week or so. If there are fish in the tank, use a test kit to test your aquarium water for ammonia. If ammonia levels are out of the safe zone a partial water change may be done to reduce the ammonia, but aggressive cleaning can remove too much bacteria and the cloudiness may return. Most major brands of aquarium suppliers sell water bacteria aids which can accelerate the process of clearing the water, but these are usually not necessary.

Another common problem that shows up from time to time is green water. The average person can probably guess that the problem is phyto plankton or free-floating algae bloom. They may not, however, understand the root cause. You see, algae blooms when it gets the resources it needs like excess nitrogen or other nutrients. More often, it means too much light in your aquarium. Like cloudiness, it can show up seemingly overnight. Algae blooms are not harmful to your fish but may be indicative of problems that are.

A hefty water change is a good idea for a green tank - really, whenever there is a problem a water change is a great first step. Even if nitrates are not the problem, it never hurts to get the levels down. Then, check the aquarium lighting. The photo period should only be eight to nine hours - even for planted or reef tanks - and the intensity should be tuned to the needs of the tank inhabitants. An appliance timer makes it simple to turn the light on and off for a desired period of time.

If the light is definitely not the problem, it could be sunlight coming in from a window. Most aquarium brands offer algaecides, but it is difficult to use them to eliminate free-floating algae because this type of algae reproduces so quickly. For sensitive or planted aquariums, the tank can be “blacked out” with a towel or blanket for a few days. A more expensive but effective option is to add a UV sterilizer to the tank’s filtration.

Clean and Clear

Any other color is drastically outside of the norm and should be investigated immediately. Any change in color can be the first indicator of something brewing that will compromise the health of the aquarium if allowed to progress. Rather than panic, a calm, methodical approach is the best way to return the aquarium to normal. With patience and direct, careful action the aquarium will look amazing in no time.

Finally, a clear tank does not always mean a healthy tank. Ammonia, nitrite, and nitrate are colorless and can build up to dangerous levels with great stealth. A new tank or heavily cleaned tank will not have the nitrifying bacteria necessary to reduce ammonia and can quickly crash with the addition of livestock. Changes in pH will not affect water clarity or color but can stress or even kill livestock. Although it looks great, a clean, clear tank still needs care and attention!