A Magherafelt farmer pleaded guilty and was fined £400, plus £31 court costs and £15 Offenders Levy, at Magherafelt Magistrates Court on Monday.
Mr Geoffrey Stewart, Luney Road, Magherafelt was fined for making a polluting discharge to a waterway.
On 5 November 2013, Water Quality Inspectors, acting on behalf of the Northern Ireland Environment Agency, inspected a waterway at Luney Bridge, Luney Lane, Magherafelt and observed brown fungus attached to aquatic vegetation in the waterway.
The source of the polluting discharge was traced to farm premises owned by Mr Geoffrey Stewart. The length of waterway affected by the discharge was approximately 1300 metres
A sample taken at the time of the incident confirmed that the discharges contained poisonous, noxious or polluting matter which was potentially harmful to fish life in the receiving waterway.
Anyone wishing to report a pollution incident can call the 24 hour Water Pollution Hotline on 0800 80 70 60.