Why is My Fish Tank Cloudy?

One of the most common issues with fish tanks is cloudy water. In most people’s minds, the ideal aquarium has crystal clear water, and as such many attempt to use chemical products such as water clarifiers in order to reestablish water clarity on their aquarium. However, that may be only hiding the symptoms of a bigger problem that can affect the health of your fish, so your goal should be to fix the underlying causes of a cloudy fish tank. There are many possible causes of cloudy aquarium water, from the setup and age of the tank to the maintenance routine and even outside influences.

When Cloudy Aquarium Water Is Normal

If you make a really big water change, or after first filling up your aquarium, the water can look very cloudy. However, it is not so much a milky cloudiness as a silvery one. The reason for that are the microscopic water bubbles that form and remain suspended in the water. It will make your aquarium look light silvery, not dull and dark, and it’s no cause for worry. After a few hours it will dissipate on its own as the bubbles either dissolve or float out to the surface.

New Aquarium With Cloudy Water

Cloudy or milky water is very common in newly set up aquariums that are undergoing the cycling process, particularly at the end of the cycle. This may make your aquarium look less than tidy, but will clear on its own once the bacterial colonies in the tank achieve balance. It is actually a good sign that your tank has finished cycling if your aquarium seemingly clears overnight.

If you just added a lot of fish to the tank, you may be having a mini-cycle. Do not try to use water clarifiers to fix this, and instead opt for extra water changes (10% to 15% twice a week) until the tank becomes stable again.

Cloudy Water After Redecorating Fish Tank

If you just added new items to your tank, milky water can be caused by inadequately rinsing it under running tap water. This can apply to filters, decorations and even gravel which hasn’t been properly cleaned. Technically your filter will remove most of the suspended debris, along with your regular water changes. This is why a new tank should be left alone for a couple of days before starting to cycle it, so the filters can remove any particulates coming from the gravel and the decoration.

Did you confirm that all your decorative items are aquarium safe? You can’t just put any piece of rock or garden decoration into an aquarium, as most will be either treated with harmful chemicals or could dissolve in water creating the cloudiness. If the water in your aquarium turns any colour not white then this is most likely the culprit.

Check every piece of decoration or rock for bits that are soft or loose, flaking off paint or any sort of discolouration or damage. If you added real shells or coral skeletons, or even reef sand, keep in mind that they will dissolve and increase the pH and the hardness. This is perfect for a marine aquarium, pretty common for a Rift Lake Cichlids tank, and bad for almost everybody else.

Only buy aquarium decoration from pet stores, and choose only pieces that are marked as aquarium safe. Otherwise you risk harming your fish and the water quality in your aquarium.

Wooden Decorations And Stained Water

Bog wood that hasn’t been sealed will release tannins into the water, which will turn it into a slightly yellowish, weak tea colour. This effect also comes with softening of the water, lowering the pH and generally making fish stronger and happier. So unless you are trying for a hard water, alkaline aquarium setup, wooden decorations are fine. The staining however can last for years since you first introduced the wood into the aquarium.

Green Water in Aquarium

If your aquarium has been exposed to natural light you may find yourself with a pretty green-yellowish aquarium. This is caused by some sort of algae bloom, which is probably one of the most annoying things aquarists need to deal with. Sadly enough, algae eating fish won’t help much here.

Your aquarium can become a paradise for algae if there is enough light and enough nutrients for algae to grow. For example, if you just used a liquid fertiliser on an aquarium that sits under a window exposed to long hours of sunlight, or long hours of artificial light. Excess phosphates or Nitrates will encourage algae bloom, and since Nitrates are the by-product of the nitrogen cycle, you will need to remove them by performing regular water changes.

Using algae killing products may sort the problem temporarily, but unless you change the conditions you will have green tank water in no time at all. Keep in mind the following formula if you have an algae bloom problem:

Light + Nitrates = Algae Explosion

Live plant can help starve out algae, as they will compete for the same resources and remove nutrients from the water quicker than the algae can use them. However, the best way to prevent algae problems in your aquarium is still not letting nitrates happen to start with:

  • Regular water changes will remove Nitrates
  • Do not overfeed your fish, uneaten food will turn into Nitrates
  • Do not overstock your tank, to avoid excess waste
  • Keep up with filter maintenance and syphon the gravel regularly to remove waste
  • Scrub the sides of the tank regularly and remove visible algae right before a water change

Regarding light, a fish tank should never be exposed to direct sunlight. Direct sunlight can make algae bloom in tanks even if it’s there just for a few hours a day.

Bad Maintenance Causes Cloudy Fishtanks

A small amateur aquarium – tank for 100 liters.
A small amateur aquarium – tank for 100 liters. (Photo credit: Wikipedia)

If you fall behind on your maintenance routine the most common side effect is milky water as algae or bacterial bloom tank place. This is compounded by floating food and waste, and any chemicals you need to throw in to keep your fish alive.

A lot of aquarium problems with water quality can be sorted by regular small water changes, proper maintenance of the filtering system and regular syphoning of waste and detritus from the bottom of the tank. However, keep in mind that changing too much water at the same time or cleaning the gravel too well can cause a mini-cycle and cloudy water on your fish tank. Small and frequent are the keywords to keep your aquarium water in perfect balance.

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