[header] How to clean a goldfish tank [title] Every week you will need to change about 25% (perhaps more depending on your water readings/types of fish you have) of the water in your tank. [substeps] How much and how often depends on the weekly test results and isn't covered in this article. This article is to give new keepers a guide on how to perform a water change in the most effective, least stressful manner. 
Less stressful for both the fish and the keeper that is. [title] Make sure you have some basic equipment.