A chemical company in Gloucestershire has been fined £66,000 following an explosion at its factory in 2006.
The incident at Biolab UK's site near Cheltenham saw chemicals leak into the River Coln, killing about 2,500 fish.
In May, the firm admitted at Gloucester Crown Court failing to take all measures to prevent the accident and failing to limit the consequences.
At Cirencester Crown Court on Friday, Judge Martin Picton also ordered the firm to pay £80,000 in costs.
The fire broke out at the water and swimming pool treatment company's factory at Andoversford on 6 September 2006.
At its height, 100 firefighters were called to tackle the blaze.
The hearing was told the company had failed to take the correct safety measures for the storage of chemicals at the site.
When fire took hold, chemicals poured into the river.
A company spokesman apologised and said the factory is now closed.
The chemicals are no longer stored at the site, he added.
An EA spokesman said fish stocks were getting healthier.