Hundreds of dead fish have been found floating near the bank of a river in far-western NSW, sparking concerns from a property owner about the safety of the water supply.

Menindee resident Wayne Marsden, whose property has access to the Darling River, made the bizarre discovery when he went to check on his water pump.

"The water is a real dirty, rotten green," he told the ABC.

Mr Marsden estimated there were between 200 and 300 dead perch on a stretch of the waterway.

"There was nothing there yesterday."

Mr Marsden has been using a water pump for his 12 racehorses but now has fears for their health.

"I don't know how much it's going to affect them," he said.

"I don't know if it's doing any internal damage or not.

"I've been pumping all the time for our animals, but it's deteriorated now and after seeing all those dead fish, I don't know what to do."

Mr Marsden said he had seen the phenomenon once before, about 20 years ago, but said the situation now was much worse.

Property owner Wayne Marsden said the last time he saw so many dead fish was two decades ago. ( Supplied: Wayne Marsden )

He suggested algae in the water may be part of the problem.

The Department of Primary Industries has been contacted for comment.

The state's far west is among the hardest-hit by the ongoing drought, with the Menindee Lakes system drying out for the third time since the turn of the century.

It has had a major impact on the local fruit-growing industry and left the region facing an economic slump.

The town has also been involved in the fierce debate about a water savings plan, which many have rejected amid claims of poor community consultation.