Restrictions on swimming at Rhyl beaches after a slurry leak have been lifted.
Fish and eels were killed after slurry from a farm leaked into the Afon Bach in Tremeirchion on Friday.
Denbighshire council put up signs advising people not to swim or paddle in the sea, or let children on the beach after bathing water was affected.
The authority said late on Friday restrictions were lifted, after further sampling of bathing water.
The Afon Bach is a tributary of the River Clwyd and its mouth into Liverpool Bay is at Rhyl.
Natural Resources Wales (NRW) confirmed water quality in the Afon Bach and River Clwyd had “improved” following the leak from a slurry lagoon.
“However, officers estimate that the impact of yesterday’s pollution may have killed up to 1,000 fish, including trout and eels,” NRW said on Saturday morning.
“Officers remain on site to monitor the works being undertaken by the farmer on the damaged slurry lagoon, and to monitor the affected rivers.”
To reduce the risk of further problems, the farmer has blocked any further possible pollution routes from the slurry lagoon, NRW added.
Nick Thomas, from NRW, said: “Our rivers and bathing waters are important to our local economy, so when pollution happens, it’s important that we act quickly to minimise the damage.
“Slurry can have a devastating impact on our rivers and the wildlife that depend on it, as we’ve seen here.”