If you want happy healthy goldfish then water changes are one of the most important activities you will engage in order to provide great goldfish care. It is even more important to do it correctly so that you do not provide unwarranted stress to your goldfish.
Do not remove your goldfish during water changes
This is one of the most common mistakes made by new persons caring for their goldfish. This method involves keeping your goldfish in the tank while changing the water. Removing your goldfish is not only unnecessary and very stressful for the fish. Removing your goldfish also normally involves your goldfish coming in contact with a net or container which rubs off some of their protective slime that protects them from diseases and supports their overall health.
What do you need for a water change?
Gravel Vacuum
Containers for holding new water and siphoning out old water (preferably 2 of the same size containers)
Chlorine and Chloramine remover
How much water to change?
It is recommended for good aquarium care to change between 10-25% of the total water volume. The reason behind this is that the chemical make-up of the water in your fish tank changes over time and changing to much may drastically change this. Goldfish are stressed by big changes in their environment and we want changes to be as slow as possible.
How to do a Partial Water Change
Fill your container with cold water from the tap
Allow the water to run for a few seconds first to ensure that you are not getting additional minerals that may have built up in the pipe.
Use cold water as this will more quickly change to the room temperature than filling with hot or warm water
I like to fill my container half way then added the recommended amount of chlorine/chloramine remover and then continue filling so that the water flow mixes in the remover. However, this step is not really necessary and it is just me being thorough.
For goldfish it is recommended that you let the water sit for 24 hours to adjust to the room temperature. Seeing that you will not be using a heater in your tank, this will insure that your tank water and new water are both the same temperature eliminating a temperature change shock for your pet goldfish.
If possible rest the empty container on the ground and place the end of gravel vacuum into container. Check to ensure that this does not come free and spill water everywhere.
Begin the siphoning action by moving the gravel vacuum up and down in the water a few times. Be careful when doing this to ensure that you do not hit your goldfish.
Once the siphon action starts be sure to go along the bottom of the goldfish tank to ensure that you are getting out as much waste as you can.
Once your container is filled remove the gravel vacuum to stop the water flow and empty the container.
Finally add your water that you have prepared to the tank.
You can do this by simply pouring the new water into the aquarium. Be gentle with this if you have decorations and gravel that you do not want to disturb.