How to Clean Fish Tank Gravel Properly With a Gravel Vacuum

The short answer

Unplug everything in the tank, then wait: Hydor and Fluval’s E heater manual give 30 minutes. Aquarium Co-Op pushes the vacuum into about a third of the gravel each water change; debris goes up the hose as gravel drops back. Move on when the tube runs clear. Refill with treated, temperature-matched water; plug in once full, filter primed, hands out.

These steps are for freshwater gravel tanks; for sand, see cleaning aquarium sand. The rest of this maintenance task is in changing fish tank water and cleaning a fish tank.

Why gravel hides the dirt, and how much to clean at once

Brian Blake of Boodleshire Aquatics, an aquarium service company: “With sand beds, the waste will accumulate on top, and with gravel, it will sink into the substrate.”

Water change percentage and gravel share, by source:

Source (type)	Gravel per session	Water per session
Aquarium Co-Op (retailer)	“about a third”	Not given
Bulk Reef Supply (retailer)	If water runs out, rest “after 5-7 days”	“Generally” not over 50%
Python (maker)	Extra-dirty tank: not all at once	Not over one third
API (maker)	Not given	10-30%, not over 30%
Aqueon (maker)	Not given	Avoid over 25%

On frequency, Aqueon: “Change 10% of your aquarium water every week or 25% every two weeks.” API’s reason for its cap is beneficial bacteria: “It is not recommended to do more than 30% because it may cause loss of bacteria and be stressful on the fish.” Aquariumscience.org, a hobby reference site, argues against weekly “deep vacuum” routines for “a well aerated, well biofiltered, mature tank”, though mulm “ON TOP OF THE SUBSTRATE” is “perfectly fine to vacuum”.

Cleaning tools and safety

A gravel vacuum, a thermometer and a bucket kept for the tank. 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.”
Gloves. The CDC: “Wear gloves when cleaning or caring for your aquarium, especially if you have cuts or wounds on your hands or if you plan to work with rough rocks or spiny fish.” Also: “People with weakened immune systems should let others in the household care for the fish tank when possible. If this isn’t possible, they should wear gloves.” and “Don’t let children younger than 5 years old clean or handle aquarium items.”

Vacuuming the gravel, one patch at a time

Mix the new water first

Aqueon: “Replacement water should be the same temperature as the aquarium water” and “Always treat tap water with a water conditioner to neutralize chlorine and ammonia before adding it to the aquarium.” Dose by the label (our water conditioner roundup compares them).

Unplug everything in the tank, and let the heater cool

Fluval’s AquaClear filter manual: “Always unplug or disconnect all appliances in the aquarium from electricity supply before placing hands in water, before putting on or taking off parts and while the equipment is being installed, maintained or handled.” Dr. Jessie Sanders, an aquatic veterinarian: “Unplug filter and lights.” and “If you have any UV lights, unplug those too.” Hydor, a heater maker, says to unplug “at least 30 minutes before any waterchange”. Fluval’s E heater manual: “If it has to be taken out of the water or when transferring or changing the water, disconnect the heater from the power source and wait for at least 30 minutes to allow it to cool down.” Our reading: wait whichever is longer, your heater manual’s time or 30 minutes; with no manual, 30 minutes, the one figure both sources give. Put on gloves (CDC, above, which also says who should not do this job).

Lift ornaments and loose rocks off the first patch

Everything stays unplugged until step 9. Co-Op says to “move any aquarium decorations away from the area you plan on vacuuming because waste likes to collect underneath them.”

Start the siphon, hose end in the bucket

Everything stays unplugged until step 9. Boodleshire: the hose end “will have to rest below the aquarium so gravity can siphon the water effectively.” With the tube filled underwater, Co-Op: “Raise the tube out of the water and above the aquarium rim until water starts flowing through the hose and into the bucket.” Then “quickly plunge the tube back into the water”.

Dig the tube down into the gravel

Everything stays unplugged until step 9. Co-Op says to “Push the siphon into the gravel or sand”. Dr. Sanders: “Press the end of the siphon into the substrate, allow the gravel or sand to move 1/4 to 1/3 of the way up the tube, then pull the siphon up, breaking the siphon.”

Let the gravel drop, then move to the next patch

Everything stays unplugged until step 9. Aqueon’s siphon-cleaner page: “Debris is pulled away with flowing water and disposed of while gravel falls to the bottom of the aquarium.” Boodleshire moves on once “the water is clear within the siphon head”. Our snail guide covers siphoning small snails out.

Stop at your water limit

Everything stays unplugged until step 9. Dr. Sanders, on the bucket: “When it gets within 3″ of the top, pull the siphon all the way out.” The CDC: “Dump tank water and clean aquarium items in a bathtub, laundry sink, or outside instead of a kitchen sink when possible.” and “Clean and disinfect sinks and bathtubs after using them to dump aquarium water or clean aquarium items.”

Refill slowly, then set the rocks back clear of the heater

Everything stays unplugged until step 9. Dr. Sanders pours slowly or uses a smaller vessel “to avoid a heavy current in your tank that may hurt your fish.” Fluval’s E manual: “Be sure there are no rocks, decorations or gravel obstructions touching the heater to create uneven heat.”

Refill done: prime the filter, then plug everything back in, hands out

Fluval: “Do not allow filter pump to run dry.” Prime the filter before you plug it in. Dr. Sanders: “Prime your filtration by pouring some tank water into the filter base.” (hang-on-back filters; canister filters vary). After a filter clean, Fluval’s AquaClear manual: “Follow operating instructions to restart and prime power filter.” Then plug in the filter and other gear; for the heater, Hydor: “The Heater can ONLY then be turned back on when the Aquarium is full and the heater is completely submerged.” The CDC says to wash your hands “with soap and running water” after cleaning the tank.

Faucet and battery gravel cleaners

Python No Spill Clean and Fill. Steps 2 and 9 still apply; plug everything back in only after the gravel tube is out (Python’s fill step 6). Step 1’s bucket does not (it fills from the faucet): Aqueon says to treat tap water “before adding it to the aquarium”, while Python’s sheet says: “If you choose to add water conditioners, you may add them into the stream of water as you are refilling the tank.” Follow your conditioner’s label. Its drain order: switch OPEN, pump to DRAIN, “Turn on the COLD water”, then the gravel tube “straight down to the bottom of the gravel and hold it still”; when the water in the tube turns clear, close the switch and move. To fill: tube out, switch closed, faucet at tank temperature, pump to FILL, then over the tank “slowly turn the switch C to the OPEN position”. Its caution: “DO NOT LEAVE THE SWITCH IN THE CLOSED POSITION FOR MORE THAN THE TIME IT TAKES FOR YOU TO GET TO YOUR AQUARIUM.” Follow the sheet for your model.

Fluval AquaVac+ (battery). “It is not recommended to use on aquarium gravel finer than 2mm. Not suitable for fine sand or fine gravel.” Unplug first (its manual repeats step 2’s caution). Fluval says its gravel-cleaner function is for “quick on-the-spot cleaning; to help extend intervals between water changes”; water changes use a separate hose mode, so our reading is that the gravel mode removes no water. “Work gravel tube so that a continuous flow of gravel is picked up and returned to the bottom, moving to new areas as water changes from cloudy to clear.” And: “Ensure that the unit is only operated under water so that the impeller does not run dry.” Plug everything back in once the unit is out (step 9).

Neglected gravel, planted beds and undergravel plates

Very dirty gravel. Python’s sheet, for its system: “Extra dirty tanks may require multiple usage to completely clean the tank. Do not clean a tank in that condition all at once.” and “If you need to repeat the procedure, wait a week before doing another water change.”
Planted soil. Fluval does not recommend cleaning its Stratum soil like gravel or sand (it breaks down prematurely); it suggests hovering a small gravel vacuum over it while gently stirring up surface debris with a turkey baster or your fingers (everything unplugged, steps 2 and 9). See our guide to planted substrate layers.
Undergravel filters. Aquarium Co-Op: “Cleaning this filter is as simple as a normal gravel vacuuming procedure” (steps 2-9).

Slips to avoid

No soap-washed bucket (tools list).
No hands in the water with anything in the tank plugged in, and no water change before the heater’s wait (steps 2-8).
No heater on before it is fully under water (step 9).

Ready to buy?

Our freshwater test kit roundup compares kits. More routines, such as cleaning a fish tank filter, are in our Tank Setup & Care section.

Frequently Asked Questions

Q. Do you take the fish out to clean the gravel?

No. Co-Op: “There is no need to remove the fish while using the aquarium siphon, since the process of catching them is more stressful than slowly vacuuming around them.”

Q. Should you rinse new gravel?

Bulk Reef Supply: “When you buy new aquarium dry sand or gravel it is highly recommended that you rinse it first.”

Q. Can you clean gravel with vinegar or bleach?

Aqua Ultraviolet, a UV sterilizer maker, says to “Avoid using bleach or vinegar at all costs” when cleaning gravel. None of the sources here gives a way to disinfect gravel; after a disease outbreak, ask an aquatic veterinarian.

Q. How do you clean gravel without a vacuum or without removing water?

Bulk Reef Supply stirs with “a long handle algae scraper, tongs, or similar device” so the filter catches the debris, calls it “not as effective”, and says: “Only stir up small areas at a time to avoid over-polluting the aquarium water”. Our reading: the filter is running, so keep your hands out (step 2). The AquaVac+ gravel mode returns the water (our reading, above).

Q. How do you clean fish tank rocks?

Bulk Reef Supply lifts “easily removable structures like rock” while vacuuming (steps 3 and 8, everything unplugged). None of the sources here covers scrubbing the rocks themselves.

Sources (17)

Aquarium Tales Team

Written and reviewed by the Aquarium Tales Team. See the About page for how we work.