The river holds a large population of wild brown trout, many of which were killed in 2006 when three tonnes of aluminium sulphate spilled into the river from the Pontsticill Water Treatment Works, which United Utilities operate on behalf of Dwr Cymru Welsh Water. The pollution turned the water white for at least downstream of the works and killed approximately 23,000 fish, including wild brown trout, bullheads, stickleback and pike, and a large number of invertebrates. Environment Agency Wales estimated that the river would take six to twelve years to recover. The trout population had resumed breeding by 2009.