Fluval U4 Foam Pad Filter Media

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Keep your Fluval U4 Underwater Filter working effectively and remove large debris with Fluval U4 Foam Pad Filter Media. Fluval U4 Foam Pad Filter Media fits inside the filter chamber to prevent debris bypass for optimal mechanical filtration. Debris like fish waste, uneaten food and other material can cause harmful toxins like ammonia and phosphate to build up in your aquarium. The foam pad has a pore size that facilitates efficient water flow with less clogging, providing long-lasting filtration for cleaner, clearer water.

Key Benefits
  • Captures large particles and debris for effective mechanical filtration
  • Custom-made to fit perfectly inside the filter chamber to prevent debris bypass
  • Helps prevent harmful ammonia and phosphate build up in your aquarium by eliminating fish waste, uneaten food, and other organic material
  • Ideal pore size for efficient water flow, less clogging and long-lasting filtration
  • For freshwater and marine environments

Compatible Products

Ensure your system runs smoothly with this Fluval Underwater Filter.

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  • Item Number
  • Aquarium Type
    Freshwater, Saltwater
  • Fish Type
    Tropical Freshwater, Marine Fish
  • Material

Do not replace all filtration cartridges at the same time. Alternate filter cartridge changes so that some older cartridges remain in use. This ensures the re-seeding of beneficial bacteria, so that colonies discarded with older cartridges will be replaced by vigorous new ones. To enhance bacterial action, pour a dose of biological aquarium supplement onto your filter cartridges each time you change the media.

  • Unplug the power cord.

  • Open the filter cover (To make the operation easier and in case the filter is positioned under an aquarium frame, tilt the filter forward until it stops but make sure there is enough electrical cord to allow the filter to pull forward).

  • Slide the foam cartridge frames out of the filter body. Keeping them vertical to avoid releasing the debris collected inside the debris receptacle. Place them in an empty bucket.

  • Remove the poly/carbon cartridge from the cartridge frame.

  • Remove the foam. Rinse the debris receptacle and the foam pads using water taken from the aquarium or replace one of the foams following the recommended replacement schedule. Do not use tap water as this will kill the beneficial bacteria in your foam. Note: Never use soap or detergents as these products could be harmful to the inhabitants of your aquarium.

  • Replace the foam pad. Make sure the foam is positioned behind the tabs on the sides of the frame.

  • With the carbon side facing out, re-insert the poly/carbon cartridge by inserting the lower end of the cartridge into the lower end of the cartridge frame then snapping the top side of the cartridge under the two tabs on the top side of the frame. Do not press too hard, as the cartridge must sit on the top of the tabs on the sides of the frame. Hint: For best results replace 1 poly/carbon cartridge every 2 weeks.

  • Slide the BioMAX cartridge out and place it in the sink or bucket.

  • Pull open the tab on the side of the cartridge, opening the cover. Rinse the BioMAX with aquarium water, never tap water, or replace half the quantity every 5-6 months. Never replace all the BioMAX nodes at one time, as valuable colonies of beneficial bacteria would be lost.

  • After rinsing, put the BioMAX back in cartridge and close the cover. For best results completely fill the cartridge with BioMAX nodes but allow the cover to close easily.

  • Re-insert foam cartridge frames into the filter with the poly/carbon pad facing inwards. Re-insert the BIOMAX cartridge into the filter making sure to properly align the hole at the bottom of the cartridge directly on the top of the impeller opening.

  • Close the filter cover and if required snap the filter body back into position on the filter bracket.

Rating: 4.5 of 5 stars 2 Reviews 2 Reviews 4.5 out of 5 Stars

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  • 4 out of 5 stars

    Great Product

    By HLR1983 on Aug 22, 2019

    Great Product been using it for years. It helps keep my sisters turtle tank clean.

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  • 5 out of 5 stars

    Getting very hard to find

    By Queenscat on Dec 15, 2017

    Obviously this filter model had some flaws since it didn't last very long - and of course I had just purchased two of them. I was very glad to be able to find the media at

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