Cloudy Water & Slime in the Aquarium Filter

When your aquarium is running properly, the water should be crystal clear, not cloudy or murky. Cloudy water could be an indication of something as harmless as dissolved particles in the tank or something as dangerous as high levels of ammonia and nitrates. The condition of your filter cartridges can also be a sign of trouble. If you notice slime on the cartridges and cloudy water, you need to take immediate steps to fix the issue.

  1. Algae Growth

    • The most common cause of slime on the filter cartridge is an excessive algae growth. Suspended algae in the water is sucked into the filter, resulting in a slimy material that adheres to the filter pads and interferes with the normal filtration of the tank. One of the best ways to fight algae growth is to add live plants to the aquarium. Those plants compete with the algae for nutrients, thereby reducing its growth. You can also add algae-retarding tablets to the aquarium and scrape any excess algae from the tank. If the tank sits in direct sunlight, moving it to a spot away from the window can also reduce algae growth.

    Test the Water

    • The cloudiness in the water could be harmless dissolved particles, but it could also be caused by harmful bacteria, or by ammonia or other dangerous chemicals. If you notice any cloudiness in the tank, you should immediately test the water. You can purchase these test kits at the pet store and use them to test for harmful chemicals like ammonia and nitrates. If you do find a problem, immediately do a 1/3 to 1/2 water change to dilute the contaminants. Then add a new filter cartridge and perhaps a new filter as well.

    Additional Filtration

    • If the water tests negative for harmful chemicals but still has a cloudy appearance, that is a sign that the filtration is not adequate to remove all the dissolved particles from the water. Replacing your existing filter with a larger model, or simply adding a second filter, is the best way to solve that problem. If you have a large tank, you may need to put one filter at each end to adequately clean the water.

    Water Clarification

    • You can clear the cloudiness from the water quickly by adding a water clarification chemical to the aquarium. You should only add that chemical after you have tested the water for ammonia, nitrates and other harmful contaminants, since the extra chemicals could interfere with the accuracy of the test. You should also add additional filtration to the tank before adding any clarification chemicals to the water. These chemicals work by causing the suspended dirt particles to form larger clumps. Those larger clumps are then captured by the filter, resulting in clearer water and a more attractive tank.