:well, you should change the water every other day anyway so not that big of a problem. but you can put some plants/driftwood/rock along shoreline to minimize the dirt.
You didn't even ask if this person has a filtration system! Sure, if they have no filtration system then I can see how it's important to change the water every other day but if you *do* have a nice filter then there is no need for changing the water so often. :( I just wish that people would ask what sort of filtration system they have before jumping all over them with the whole "change the water every other day" bit.