An iron sludge discharge from a "no longer fit for purpose" water treatment plant operated by Uisce Éireann was the cause of an "ecological tragedy" that wiped out all fish life over a 2.6km river, a court has heard.At Ennis District Court, judge Alec Gabbett fined Uisce Éireann the maximum fine allowed of €5,000 for each of the two pollution discharges from the Ballymacraven water plant near the north Clare town of Ennistymon on 2 May and 18 May last.