Well...IMO, thats up to the person. I try do a 10%, weekly but most of the time its more. I dont add supplements or liquid food. When I do a water change, its hard to just do 10%, cause I try to siphon all the debris and clean the rocks, its hard to stay with in that 10%. If Im lazy then its just 10%. I see why others needs to do a bigger percentage when having to do all those stuff.