I have a Whisper mini filter good for 15 gallons. There's only about 6 1/2 gallons in there now and once they more that will drop to about 5 gallons. I plan on changing the filter every other month or as needed. It has a drop in type filter that kind of clips secure and is able to be rinsed out if it starts to get icky too quickly. (I just use the treated tank water in a seperate bowl and swish it around to clean it up a bit between water hanges.)
::Actually, I don't think it would. But if you have a filter I don't think it's a problem. Or if you don't just get the filter, or after you get all the water out clean the tank and rinse the gravel just like I do.