How to Clean an Aquarium (Without Killing the Filter)

Cleaning a tank is not about scrubbing everything sterile — it is about removing waste without destroying the bacteria that keep fish alive.

A clean aquarium is not a sterile one. The surfaces, filter and substrate hold the bacteria that process fish waste, and scrubbing them away causes more problems than it solves. The goal is to remove waste while protecting the filter.

Quick answer

Change water, vacuum part of the substrate, wipe the glass, lightly rinse the filter

Weekly: 25% water change + gravel vacuum.
Glass: Wipe with a sponge or scraper as needed.
Filter: Rinse in old tank water only when flow slows.
Never: Strip the tank or replace all media at once.

The weekly routine

Switch off the filter and heater if the water will drop below them.
Wipe the glass with an aquarium sponge or scraper, inside and out.
Change 25% of the water, using a gravel vacuum to clean part of the substrate as you go.
Clean décor lightly — a soft brush removes algae without stripping it bare.
Refill with dechlorinated water matched to temperature, then restart the equipment.

The filter: handle with care

The filter is where the good bacteria live, so clean it only when flow slows, and rinse the media in a bucket of old tank water — never under the tap. Replacing all the media at once throws your cycle away and produces an ammonia spike. See filter maintenance.

Common mistakes

Full teardowns. Emptying and scrubbing everything kills the cycle.
Tap-water rinsing. Chlorine in tap water kills the bacteria.
Over-cleaning gravel. Deep-clean only part of the substrate each week.
Soap or detergents. Never use them on anything that goes in the tank.

The weekly routine

Switch off the filter and heater if the water will drop below them.
Wipe the glass inside and out with an aquarium sponge or scraper.
Change 25% of the water, using a gravel vacuum to clean part of the substrate as you go.
Clean décor lightly — a soft brush lifts algae without stripping it bare.
Refill with dechlorinated water matched to temperature, then restart the equipment.

The filter: handle with care

The filter is where the good bacteria live, so clean it only when flow slows, and rinse the media in a bucket of old tank water — never under the tap. Tap water contains chlorine, which kills the bacteria and crashes your cycle. Replacing all the media at once does the same thing, so if media must be changed, stagger it over weeks.

Glass, décor and plants

Wipe the glass with an aquarium sponge to remove algae before it hardens; a plastic scraper handles stubborn spots on glass but not on acrylic. Décor can be scrubbed lightly in old tank water, though a little algae on wood and rock is natural and grazed by fish. Live plant leaves should be left alone — a soft brush only where algae is thick. Never use soap or household cleaners on anything that goes in the tank.

Cleaning the substrate

Vacuum part of the substrate each week rather than deep-cleaning the whole bed at once, so you remove mulm without disturbing all the bacteria and plants. Push the siphon into gravel and lift so waste is carried away; with sand, hover just above the surface and stir the top layer occasionally. A shallow, tidy bed is easier to keep clean than a deep one.

Mistakes to avoid

Full teardowns. Emptying and scrubbing everything kills the cycle.
Tap-water rinsing of filter media — chlorine kills bacteria.
Over-cleaning gravel in one go; rotate the sections.
Soap or detergents — never, on any tank equipment.

A clean tank is not a sterile one. Aim to remove waste and keep water clear while protecting the bacteria and the fish's calm, and the tank will run itself with little more than a steady weekly routine.

The kit worth keeping

You need very little: a gravel siphon, two buckets (one for old water, one for fresh), an algae sponge, a plastic scraper for glass, and an old toothbrush for awkward corners. Keep a dedicated set that never touches soap or household cleaners, and mark which bucket is which to avoid any trace of detergent reaching the tank. Having the tools ready makes the routine quick enough to actually do every week, which is the single biggest thing that keeps a tank clean and stable.

How often should I clean the tank?

A weekly water change and gravel vacuum suit most tanks; wipe the glass and clean the filter only as needed.

Can I clean everything at once?

No — it removes the bacteria and stresses the fish. Clean in stages on rotation.

Do I need to remove the fish?

Not for a normal clean. Only remove them for a full rebuild, and keep them in tank water meanwhile.

Tools for this guide

Water change calculator

Sources and research notes

Cleaning practice follows standard fishkeeping guidance; the key point is protecting the biological filter while removing waste.

Written and edited by the Tankwise Editorial. Every guide answers one real fishkeeping question, is checked against the sources listed above, and is updated when guidance changes. We are an independent editorial desk, not veterinary or aquarium professionals — read how we research and update our guides.