How To Change The Water In A Fish Tank

How To Change The Water In A Fish Tank

Keep the water in your fish tank clean for healthy happy fish

This needs to be done every 2 – 3 weeks.

You will need:

  • gravel syphon
  • jug
  • 2 buckets

Turn all the electrics to the tank off and remove the lid.


As all the muck sinks to the bottom of the tank you will need a gravel syphon to remove it from the gravel; using a jug to scoop out the water will only result in taking out the clean water from the top of the tank.

Place your bucket which will collect the dirty water lower down than your tank.

Fully submerge the syphon and gently shake it up and down; then it should just start to syphon.

Crunch the nozzle into the gravel; it will pick out the dirt and the heavier gravel will just fall back. Go through the whole tank. Remove about 25% of the water.

Have some tap water ready in a bucket, making sure it is the same temperature as the water in the tank. Add de-chlorinator to the water in the bucket to the dose advised on the bottle, we are adding 10ml. This will remove any heavy metals present in the tap water. Also add the recommended dose of Filter Active to the water in the bucket; this helps build up the biological bacteria lost during the process. We are adding 5ml.

With a jug gently pour in the water; if you pour it over an ornament the water disperses gently and doesn’t shock the fish. Don’t pour it over the filter as this disturbs the bacteria. Fill the tank to its previous level.

Replace the lid and turn on the electrics.

Profile Image Angela Slater

Angela Slater

Daughter of a farmer and market gardener so have always had a connection with the outdoors, whether it was keeping animals or producing fruit, vegetables and cut flowers. Along with my work at Hayes Garden World I also have a smallholding, mainly breeding rare breed pigs. I gained an HND and BSc in Conservation and Environmental Land Management, as a result I am an ardent environmentalist and have a keen interest in environmentally friendly gardening. In my time at Hayes I worked for several years in the Outdoor Plant and Houseplant areas.