Imagine that you have been confined to a small chamber. You try to look outside, but the images are warped, as though seen through a giant, funhouse mirror. Your own feces, urine and uneaten food stack up and rot around you at a shocking rate, causing bleeding ulcers on your skin and burning your eyes, nose and lungs - breathing becomes harder and harder. You constantly shiver at the cold. Your chamber is cleaned every week, but only partially, and the toxic filth just stacks higher every time. You will languish in these conditions for a few years and then die.
This sounds horrific, doesn't it? But sadly, despite what uninformed pet store employees may tell you or what the packaging on fish bowls may say, this is the "life" of a fish in a bowl.
Given the above explanation of partial water changes as an inadequate solution to waste in a fish bowl, you might think that simply changing all of the water, and thus removing all of the waste, is a solution.
However, 100% water changes are dangerous in their own way and bring a completely new set of problems. Any change in the chemistry of the water a fish lives in must occur incredibly gradually. Sudden changes are at best dangerous, and at worst lethal. (See A RULE TO LIVE BY) One cannot guarantee that the chemistry of the water you are changing is teh same as that of the water you are removing, and thus a sudden, 100% water change can be very dangerous to your fish. For more information, see our WATER CHEMISTRY page.