Rinse in tank water
Rinse media in water you removed from the tank. Chlorine, chloramine, and temperature shock from tap water can kill the bacteria.
Routine care
Cleaning Your Filter Safely
Your filter holds most of the bacteria that keep the water safe. Clean it to restore flow, not to make it look new: rinse in old tank water, keep the bio media, and restart it properly.
Ground rules
Protect the bacteria
A brown, dirty-looking sponge is normal. The goal is good flow with the bacteria still in place.
Never replace it all
Swap no more than about half of the media at once. Wait a few weeks before replacing the rest.
Clean for flow
Clean when flow slows down, not when the media looks dirty. Squeeze and swish, do not scrub it white.
Keep it wet and quick
Keep bio media in tank water while you work. Media that dries out or sits in a switched-off filter for hours loses bacteria.
Before you start
What you need and how often
Plan filter cleaning for a water change day so you have removed tank water ready.
Bucket of tank water
Siphon a few gallons into an aquarium-only bucket before you open the filter.
- Use removed tank water, not tap
- Saltwater: rinse in removed saltwater too
Brushes and a towel
Cheap tools make the parts you cannot reach easy to clean.
- Long flexible brush for tubing and intakes
- Small brush for the impeller well
- Towel or tray for drips
Replacement media
Fine floss and chemical media wear out. Biological media rarely needs replacing.
- Fine floss or pads for polishing
- Carbon or other chemical media, used per the label
- A spare sponge or bio insert that stays put
Starting points
Every tank is different. Let flow tell you when it is time.
- Hang-on-back: check every 2 to 4 weeks
- Canister: every 1 to 3 months
- Sponge filter: when bubbles or flow slow down
- Reef filter socks: every few days to a week
Step by step
How to clean each type
Always unplug the filter first. Check your filter's manual for parts that are specific to your model.
HOB filter
Lift out the cartridge or sponge and rinse it in the bucket.
- Squeeze the sponge until it runs mostly clear
- Replace a cartridge only when it falls apart or will not rinse clean, and keep a sponge or bio insert so bacteria stay
- Wipe sludge from the box and intake tube
Canister filter
Close the valves if it has them, disconnect, and carry it upright to a tub or towel.
- Rinse sponges and coarse pads in tank water
- Leave ceramic rings alone, or give a clogged basket a gentle swish
- Replace fine floss and check the lid O-ring is clean and seated
Air-driven sponge
Turn off the air pump and slide the sponge off.
- Squeeze it in tank water several times
- With two sponges, clean one per visit
- Check the airline and check valve for kinks or clogs
Impeller and tubing
Gunk on the impeller and slime in the tubing slowly choke flow.
- Pull the impeller and wipe it and its well clean
- Handle the shaft gently: some are ceramic and snap
- Brush tubing and intakes until the brush comes out clean
Restart
Prime and check
Most pumps should not run dry. Get water in before you plug it back in.
Prime first
Fill a hang-on-back box with tank water. Prime a canister with its primer or by filling it, as the manual says.
Plug in and burp
Gurgling and sputtering mean trapped air. Gently rock a canister or top off a hang-on-back box until flow is steady.
Watch for leaks
Check hoses, valves, and the lid over the next hour. Listen for rattling that may mean a worn impeller.
Test in a few days
After a big cleaning, check ammonia and nitrite. Any reading above zero means the bacteria were set back.
Avoid these
Common mistakes
Most filter crashes happen right after a cleaning that was too thorough.
Rinsing under the tap
It looks cleaner, but it can wipe out the bacteria and start a new ammonia spike.
Soap or hot water
Never use soap, bleach, or household cleaners on anything that goes in the tank. Hot water kills the bacteria too.
Too much in one day
Do not deep clean the filter, vacuum all the gravel, and replace media on the same day.
A long shutdown
Water in a filter left off for hours goes stale. Rinse the media in tank water before restarting it.