How to Change Water in a Tropical Fish Tank

Updated April 17, 2017

Carrying out partial water changes for your tropical fish tank is essential for your pets' health and survival. If you let waste and decayed food remain in it for too long, the water will become cloudy and eventually, ammonia will build up and kill them.

Here is how to change the water in your tropical fish tank so you can avoid this.

Fill up at least one five-gallon bucket with tap water, preferably water that is room temperature. The amount of water you are treating should constitute about 20 per cent of your total aquarium capacity. Hot water contains less oxygen. You are going to use this water to replace the five gallons of tank water you are going to remove in the aquarium cleaning process.

Treat the water you have filled in your bucket or buckets so that it is suitable for your fish to live in. Add water treatments or conditioner as necessary--a few drops of Prime usually does the trick. You may want to add a pinch of salt as well, as some tropical fish, such as guppies, thrive with some in their habitat.

Add to your bucket or buckets of water half a spoon each of PH neutraliser to ensure the PH level is around 7, which is ideal for most tropical fish. Your tap water may be below that--too soft/acidic--or too high--or too hard/alkaline. You may want to test your tap water with an aquarium water testing kit when you are changing your tank water for the first time--the PH may be ideal as it is.

Wait about 12 hours for the chemicals in your bucket or buckets of water to do their jobs and remove all the chlorine, metals and other potential toxins in your tap water and make it safe for your fish to live it. This also allows enough time for the water to become room temperature.

Use the siphon to suck about 20 per cent of your tank water and dispose of it in an empty bucket or buckets. To start the siphoning process, pump the pump that may be attached to it or tap the bottom of the device several times on the floor of the fish tank. The water will begin to flow upward and out of the tank. Move the working siphon along the floor of your tank and under the gravel, if you have any. You will begin to see specks of waste rising fast and through the tubing until it fills up your bucket or buckets. Do not be alarmed if the water is cloudy--this is normal and you are remedying the situation by changing the water.

Fill your aquarium with your prepared water in your buckets. Make sure not to spill any. Do not top the tank off--you will likely make a mess and furthermore, many fish are prone to jumping.

Prepare more buckets of water for your next water change and store in an enclosed space, such as a cabinet, until it's time to repeat the process all over again.


You may also opt to start the siphoning by sucking on the opposite end of the tube, although this is not very sanitary.

Things You'll Need

  • Siphon
  • At least two 5-gallon buckets with strong handles
  • Water treatment--such as Prime
  • PH neutraliser
  • An aquarium water testing kit (optional)
  • Aquarium salt (optional)
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