Please can anyone explain why I have lost 90% of my pond fish ?
Pond is built above ground, is 8 feet x 4 feet x 2 feet deep,
has a pump aerater on 24/7 and a pumped waterfall running for 2 periods of 4 hours running through a large filter/ultra violet unit. Pond contains much plant life and appears to be in balance, water is not dirty and does not smell.
Fish have lived and bred successfully for 18 years.
Over night for no apparent reason 33 goldfish ranging from 6 - 9 inches in lentgh have died - no signs of illness, damage or (before) distress have been noticed.
Nothing has been introduced (plants or fish) in the past six months.
I would be grateful for any ideas as to why these fish have died.
Thanks AWood (England)