Residents in part of Wanganui's St John's Hill suburb are being urged to be careful what they put into their stormwater drains.
Any chemicals and cleaning agents used to clean driveways, roofs or cars in part of the hillside suburb will end up in Rotokawau pond and, consequently, Virginia Lake.
The pond is in a small reserve at the end of Norfolk Dr off Virginia Rd and, in the past, chemical pollution killed fish and left the pond with "an unsightly, unnatural colour and smell".
A Wanganui District Council leaflet describes the catchment as small but an aerial view shows it takes in a residential swath of the hillside suburb.
It extends from Mannington Rd, along Virginia Rd and then across the northern boundary with Virginia Lake and back up Great North Rd.