How to clean aquarium sand

Aquariums are great when they’re clean, but they need frequent maintenance to keep them that way. Here’s how to clean the sand.

Sand or gravel is often the first decoration you’ll place into your aquarium. Fish occur naturally over sand, gravel, silt, stones and rocks, and many species are adapted to sift sand to find food. It gets dirty quickly though.

Sand sifters

Add sand sifting fish species like Corydoras catfish, which use their short whiskers to probe the sand for food. Add a group of five to tanks over 60cm in length, and they will sit on, swim over and sift through the sand bed all day long, keeping it turned over and helping to keep it clean. Corydoras and suckermouthed catfish are often referred to as cleaner fish, although they can’t survive just on scraps and should be fed a sinking food designed specially for them.

Keep Corydoras over a dirty substrate and they can get infections, which wear away their delicate barbles. So you’ll need some sand cleaning apparatus too.

Gravel vacuum

Gravel vacuums are wonderfully simple devices which keep aquarium sand and gravel clean. A combination of a flexible syphon tube and a wider diameter pipe, gravel vacuums suck gravel and sand up the wide pipe, tumbling it and releasing the dirt and debris. Dirt floats up the tube and into a bucket, and the substrate sinks back down to the aquarium bottom.

Gravel is easier to vacuum than sand because it’s heavier. Being fine, sand can get sucked up and removed by a gravel vacuum, but with practice the vacuum can be hovered slightly higher above the sand and it will be lifted, cleaned and dropped back down. 

Power vacuums

If syphoning isn’t your thing, the Fluval AquaVac Plus is a battery powered gravel vacuum which can either trap waste and return clean water to the tank, or connect to a hose to remove dirty water in a water change. Suitable for sand or gravel, just hover the device slightly higher if cleaning fine sand. 

Elbow grease

Sand sifters and syphons can be given a hand by you running your fingers through sand beds regularly. If you don’t mind getting a wet arm, rake the sand bed with your fingers, turning it over and dislodging dirt and debris. Combine this with a water change and mechanical filter clean, and dirt will be removed permanently. Wash hands afterwards and arm yourself with a towel to stop drips.

Black sand

Fine sand can compact and turn black if not cleaned regularly. The black colouration comes from anaerobic bacteria, taking up residence in dirty sand and producing a rotten smell. Anaerobic conditions are bad for fish and the health of the aquarium, so deep sand beds should be avoided and shallow, frequently cleaned sand is the order of the day for a healthy aquarium. 

5 Golden rules

  • Not all sand is the same, so only use sand which is labelled as aquarium sand. Avoid builders sand as it will be dirty and will adversely affect pH. 
  • Clean sand thoroughly before you place it in the aquarium. New sand can turn water cloudy, so rinse in a bucket for adding it.
  • Use a thin layer. Sand beds over 2.5cm deep are more prone to compacting and turning anaerobic.
  • Don’t mix fine sand with coarser grits and gravels as the sand will work its way to the bottom, leaving the larger gravel on top. 
  • Use a combination of substrate dwelling fish and regular gravel vacuuming to keep your sand clean and pristine.  

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Jeremy Gay is an author and freelance aquatic specialist. A former editor of Practical Fishkeeping magazine, he offers a wealth of experience on all things aquarium and pond.


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