How to Clean Algae Off Fish Tank Filters

Written by tom wagner
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How to Clean Algae Off Fish Tank Filters
This is the last thing you want to find in your aquarium. (alga image by laviniaparscuta from

Although algae is more likely to grow on the sides of your aquarium or on the surface of the water, the filter of an infested fish tank can also collect it. Excess algae growth can result from poor circulation in the tank, an un-cycled aquarium -- a deficiency of "good" bacteria due to excessive cleaning or water changing -- organic build-up resulting from infrequent vacuuming of waste -- or low oxygen levels.

Skill level:

Things you need

  • Siphon
  • Medium bowl
  • Bucket or large bowl
  • Scrub brush
  • Bottle brush

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  1. 1

    Remove two cups of water from the aquarium with either a siphon or a scoop of some kind. Put this water into a medium-sized bowl. You will use this water to clean the filter. Tap water contains chemicals that can harm your fish -- and using distilled water to clean the filter will remove an excessive amount of the beneficial bacteria. You want to keep as much of this bacteria as possible. Leave this bowl in the sink.

  2. 2

    Unplug the filter's power cord.

  3. 3

    Remove the side-mounted filter apparatus from the aquarium. Transfer it to a bucket or large bowl, to prevent dripping aquarium water throughout your home. Carry it to the sink.

  4. 4

    Remove the rectangular filter from the filter apparatus. Place it in the bowl of aquarium water. Use your hands to rub away scum and pick out larger accumulated algae colonies: Then squeeze the sponge filter repeatedly -- while holding it under the water. The water should cloud significantly. Replace the sponge filter, if it is torn or has holes in it.

  5. 5

    Disassemble the filter apparatus. It is usually between three and five pieces; these will come apart easily. Use a small scrub brush to clean algae off the exterior of the plastic pieces. Use a bottle brush to clean out the insides of the tubes.

  6. 6

    Reassemble the apparatus. Replace the rectangular sponge in the side-mounted unit and remount it onto the aquarium.

  7. 7

    Refill the apparatus with water from the cleaning bowl -- if the water does not contain floating or suspended particles -- otherwise, use clean, room temperature distilled water, or tap water -- once you treat it with a product that removes harmful chemicals.

Tips and warnings

  • Keep between one and three plecostomuses or snails in your tank, depending on the aquarium size, to prevent algae build-up. Be sure to remove excess snails; they reproduce quickly.
  • Remove any dead fish as soon as possible. Necrosis provides vast quantities of nutrients that encourage algae growth.
  • Keep your aquarium away from direct sunlight, which also encourages rapid growth of algae. If the aquarium is beside a window that receives direct sunlight, close the shades during the brightest part of the day. Keep your aquarium light on for no more than 10 hours a day.
  • Do not clean your aquarium with too much zeal. Removing every bit of algae by scrubbing the tank --- once you have removed the fish, naturally --- in addition the scouring your artificial plants and rocks can result in rapid growth of algae, especially in saltwater aquariums. You won't be able to remove every single alga, and when there is no competition for nutrients, the survivors will flourish. When you scour your tank, leave a few rocks or pieces of coral behind, un-scrubbed, to keep a small colony of healthy algae in your aquarium.

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