How to Clean a Fish Tank Filter: Sponge, Hang-on-Back and Canister

Unplug, then bag the sponge underwater

Unplug the appliances in the tank before your hands go in (Safety, above). Aquarium Co-Op uses a fish bag or zip-top bag: “fill it with water inside the tank, and gently place the sponge into the bag while it’s still underwater”, so less waste escapes.

Take the sponge off its frame

Co-Op says to “remove the strainer basket, base, and other components from the foam sponge before cleaning it”. hygger’s HG120 manual, as transcribed in our sponge filter roundup, warns: “The round hollow tube and bulkheads are one piece;do not separate them to avoid damage.”

Squeeze it in tank water until the water is no longer brown

Co-Op: “Squeeze the sponge several times inside the bag until the water inside is completely brown”, empty the bag into a bucket, refill it from the tank, and repeat about three to four times until the water is no longer brown. hygger: “Don’t use tap water or hot water to clean the biochemical sponge filter.” Co-Op’s founder recommends water “roughly the same temperature as the tank water”, since “very hot water may damage the bacterial colony”.

Scrub the frame and refit it upright

Co-Op says to “rinse the other filter components with water and use a toothbrush to scrub them if needed”. Aqueon, an aquarium equipment maker: “Don’t use buckets, scrub pads or any other equipment on your aquarium that have been used with soap or other chemicals.” hygger says to keep the HG120 vertical, otherwise “the pipe will be blocked by the ceramic pearls.”

Unplug it

Fluval’s AquaClear manual: “Always unplug power filter prior to cleaning.”

Empty the case

Fluval: “Remove cover, filter basket, and discard water remaining in the filter case.”

Swish the media in tank water

Aqueon’s cleaning checklist: “Take out any biological filter media and place it in a bowl or container of aquarium water”, then “Clean or replace any mechanical filter media. Replace any chemical media such as activated carbon.” The AquaClear manual names no rinse water for media; Fluval’s 07 manual says: “Rinse biological media with aquarium water, never tap water, or replace as required.” Co-Op says to “try to keep the filter media wet to prevent drying, which may decrease the beneficial bacteria count”.

On a Penguin Bio-Wheel filter, swap the cartridge and leave the wheel

Marineland’s Penguin manual (dated 09/04) says to replace the cartridge every 2-4 weeks, and: “NEVER clean or replace BIO-Wheel (unless damaged). Discoloration is normal and desirable. If excessive buildup occurs, rinse gently with room temperature dechlorinated water.” For cartridges in general, Aqueon’s do’s and don’ts differ: “Change filter cartridges at least once a month. Check them weekly and rinse as needed.” Modest Fish (its Penguin 375 review), a review site quoted in our filter roundup, warns that a change means “you’ll be throwing away all of the beneficial bacteria” on the cartridge; the roundup notes the “Bio-Wheel keeps a biological stage separate from the cartridges”.

Rinse the case and impeller

Fluval: “Thoroughly rinse collected debris from the case, impeller cover and impeller assembly in clear lukewarm water.” “Do not use soaps or detergents.” On an AquaClear, every three months, “Remove motor by twisting a ¼-turn gently in the direction of the arrow on front.” “Ease motor down slowly to prevent damage to the filter and motor guide.” Then “Pull impeller out of impeller well and rinse to remove accumulated slime deposits”; “A cotton swab or impeller well brush can be used to remove more stubborn deposits.” The Penguin chart says: “Clean Impeller monthly”.

Brush the intake tubes

Fluval: “The intake “U” tube and extension tube can be cleaned with a filter stem brush to remove any buildup of deposits.”

Fill the case before you plug it in

Fluval: “Fill filter case completely with water.” Dr. Sanders says to prime “by pouring some tank water into the filter base.” Once plugged in, “Allow 30-45 seconds for priming.” It warns: “IMPORTANT – DO NOT OPERATE FILTER WITHOUT WATER” and “Do not allow filter pump to run dry.”

Close the valve, then unplug

Fluval: “Close the AquaStop valve by lifting the lever all the way up.” Then unplug the power cord.

Release the valve and carry it upright to a sink

Fluval: “Lift the locking lever to release the AquaStop valve.” “Hold the unit by the canister, not the cover”, and “Be sure to keep it upright to avoid spills”.

Open it and lift out the media

Fluval: “Release the lift-lock clamps; then push down on clamps to lift the cover/pump housing off the canister and set it aside.” “Remove media cover, then using the center handle remove media baskets from canister. Next, lift and remove prefilter basket and place all media components in a sink or bucket.” Then “Tilt the canister over a sink or drain and pour out all remaining water.”

Sort the media

Fluval: “Chemical media cannot be cleaned.” “Rinse biological media with aquarium water, never tap water, or replace as required.” “Never replace all biological media at one time, as valuable colonies of beneficial bacteria would be lost.” “Rinse foams using aquarium or de-chlorinated tap water or replace foams as needed.” “NEVER use soap or detergents as traces of cleaning products could harm fish.”

Rinse the canister with water only

Fluval: “Rinse the interior of the canister with clear water. NEVER use soap or detergents when cleaning canister or rinsing prefilter or media baskets. Traces of cleaning products may remain on surfaces and damage sensitive fish tissues.” Co-Op adds: “Follow the manufacturer’s instructions to keep any sensitive electronic components dry.”

Check the impeller gently

Fluval: “The impeller fan has a ceramic shaft, which is resistant to wear and tear in use, but is still fragile. Handle carefully during maintenance.” If it needs cleaning, “Rinse it under clean water.”

Reassemble without filling the canister with water, then let it fill

Fluval: “DO NOT FILL CANISTER WITH WATER WHEN RE-ASSEMBLING UNIT”. “Place rinsed and filled media baskets back in canister”. Lubricate the motor head gasket “using only silicone based lubricant”; “Do NOT use petroleum jelly, vegetal or animal based products.” “Use the lock-lift clamps to close the cover securely.” Then “Place the unit back in position; re-insert the AquaStop valve, and push down the locking lever to lock it in place.” “Push down on the valve lever to open the AquaStop valve.” “Allow the canister to fill completely, then plug the power cord back into the electrical outlet.” Fluval: “IMPORTANT: If the canister is not full before the filter is plugged in, it may not work properly. The filter unit should never be allowed to run dry. Running the unit dry may result in damage to the motor.” If the hoses were taken off the valve or the system lost its vacuum, “the canister will not fill automatically. Use the instant-prime handle to fill the canister.”

Clean the intake and hoses on their own schedule

Fluval: “Pipes will gradually block with protein slime and waste.” For the hoses: “A good time to do this is during a major water change. To clean, rinse under running tap water; if necessary use an appropriate Fluval Cleaning brush”.