How to clear green aquarium water

Powder Blue Tang

Step one: Keep your cool!

Once fish disappear in green water, we often act with a sense of urgency. We tend to overcompensate with large water changes and other big ideas. In most cases sudden BIG CHANGES in the aquarium have negative consequences.

The larger the change, the greater the resulting biological imbalance.

Small, gradual actions allow for the fish tank to adjust more quickly to the biological changes.

Clear cloudy aquarium water, remove nitrates and simplify aquarium maintenance

The most immediate threat of green water is oxygen depletion. Green water is a free-floating algae bloom and algae takes up oxygen just like any other plant. Creating surface agitation in the aquarium can easily increase oxygen levels. Adjusting the filter return to increase surface water movement will increase available oxygen in the tank. Further, the tank temperature can be lowered a few degrees increasing the water’s capacity to hold oxygen.

Follow these steps to clear green aquarium water:

  • Keep water changes at about 15 – 20% every other week.
  • Remove waste from the tank with an aquarium siphon.
  • Remove nitrates, as this is the primary food source for algae.
  • Cut feeding to once every other day. Don’t feed more then the fish can eat within about one minute.
  • Decrease the lighting period to no more then 6 hours per day.

Following the steps above will put your aquarium on a path to recovery.

Preventing green water:

Once the tank has cleared up future green water outbreaks can be avoided by limiting the amount of waste in the aquarium and keeping nitrates as low as possible.

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10 thoughts on “How to clear green aquarium water

    • Scott @ Algone
      Scott @ Algone says:

      The cause of green aquarium water and algae growing in the fish tank are the same. High nutrients are generally to blame. You should make sure nitrate is low as this is a primary food source for algae. Nitrates are the direct result of decaying organic waste in the tank. Usually this is food either uneaten left to decay, or fish excrement. Either way, it’s generally good practice to feed a maximum of once per day sparingly. It’s also perfectly fine to feed once every other day while trying to clear the aquarium. Fish have a very slow digestive system and will do well on the reduced amount of food.

  1. judy schuster says:

    We have done everything that u suggest to clear the green water….have taken water samples to pet store and they tell us our water tests perfect….this has been going on for 3 months…help!!!! Thank you

  2. Thilo @ Algone
    Thilo @ Algone says:

    The best chemical to maintain good health is probably the ones that prevent issues. The term chemical of course used loosely here, but activated carbon, water conditioners, and products like Algone, literally anything that removes waste and pollutants.