Just curious... does ball size matter?
I would think that having big balls would allow more flow in between them... therefore staying cleaner in the long run. So in that case, people with smaller balls spaced close together would collect more detritus and would therefore need to clean them more often.
Another thought... some people keep their balls completely submerged and some keep their balls moist with water flowing over them. Is one method better than the other?
In case anyone is interested... you can get
blue balls on sale at ebay.
http://cgi.ebay.com/5-Gallons-300-La... QcmdZViewItem
.