Water changes are necessary for the health and survival of your fancy goldfish. Before you read the rest of this article, we recommend that you read our article on the nitrogen cycle. You can read our article on the nitrogen cycle by clicking here, on the red word "here".
During a water change you will replace a portion of the dirty water. Over a few days nitrates will begin to build up in the water of your goldfish aquarium or pond. If the nitrates are not manually removed they will build up to dangerously toxic levels and poison, or maybe kill, your fish. Unlike other fish, goldfish produce almost 10 times the amount of ammonia as other fish. This means that the water in your goldfish tanks will need to be changed more frequently, and that a larger portion of the water needs to be changed, in comparison to other fish tanks. Fortunately, goldfish are not nearly as sensitive to large water changes as other freshwater fish, and a large water change will not shock goldfish.
The best tool any goldfish owner can have is a water changing hose that can be attached to the sink. These hoses can be bought almost anywhere fish are sold. Use your water changing hose to drain 50-90% of the water in the tank. The fish do not need to be removed. Then stop the hose from removing any more water. Add the correct amount of water conditioner before refilling the aquarium. Then refill the tank with clean water to replace the water that you removed. This process must be repeated at least once a week, and it may need to be done more than once a week if necessary.