Some common reasons why fish die are:
-build up of toxins caused by lack of filtration, overfeeding or too many fish in the system
-poor water conditions or sudden changes to water conditions
-low oxygen in the water from lack of aeration
-predators such as birds or mammals
-parasites or disease
Keeping fish in ponds is easy with the right equipment. If you loose fish speak to your local retailer and identify some of the possible reasons why. In most cases simple changes to your system will get you back on track and give your fish a safe environment to thrive.