"Cleaning" the water is a little more complicated than that ... good news is that, if you get it just right, you may NEVER need to EVER change water!!!

But before we go into that, "cleaning" your water consist on MECHANICAL, BIOLOGICAL, and CHEMICAL filtration.

MECHANICAL = removing the "visible" waste, usually by use of a filter material, e.g. sponge.

BIOLOGICAL = removing the disolved waste, usually by use of bacteria in your tank, e.g. live rocks, deep sand beds, macro algea

CHEMICAL = removing disolved waste that is not biological in nature. i.e. cannot be broken down by bacteria. Usually by using activated carbon.

Now, there are many different ways to achieve the above. The most popular methods are by protein skimmer + live rocks + deep sand bed + macro algea + good water flow.

Hope this gives you a place to start more researching!!