I only fished the Taupo area so I'm not 100% sure on the rest of NZ
"Strike indicators
When you use a stike indicator, you can add only a dye or line floatant.
A strike indicator is any synthetic or natural yarn and its means of attachment to the line or cast used by the person fishing as an aid to detecting a strike. It does not include any other material or any other object attached to the line or cast, or any synthetic or natural yarn to which has been added any material or chemical (other than a colour dye or surfactant line flotant preparation)."
http://www.nzfishing.com/Regulations/RegulationsTaupo.htm