@fantail76 I'm sorry about your fish... it's always sad to lose one.
We often hear "this fish was in this pond for X number of years, nothing changed, not sure what happened". Well, something actually DID change... the size of the fish. As fish grow, their biomass increases exponentially and consequently so does the amount of waste they produce. Every pond will have a "tipping point" - that moment when one factor increases to the point that all the other factors can no longer maintain balance. Water volume, aeration, number and size of fish, plants, weather... a number of things can be the "last straw" so to speak.
Even at 1300 gallons, your pond is too small for full grown koi... and every koi eventually becomes full grown! Are your other fish all koi as well? If so, you may want to give some thought to re-homing some of them. A pond your size would be ideal for goldfish - and you can have lots of those! As they stay smaller, they are much better suited to most garden ponds.
Here's a chart that was very eye-opening to me about the difference between fish as they grow:
russellwatergardens.com
We often hear "this fish was in this pond for X number of years, nothing changed, not sure what happened". Well, something actually DID change... the size of the fish. As fish grow, their biomass increases exponentially and consequently so does the amount of waste they produce. Every pond will have a "tipping point" - that moment when one factor increases to the point that all the other factors can no longer maintain balance. Water volume, aeration, number and size of fish, plants, weather... a number of things can be the "last straw" so to speak.
Even at 1300 gallons, your pond is too small for full grown koi... and every koi eventually becomes full grown! Are your other fish all koi as well? If so, you may want to give some thought to re-homing some of them. A pond your size would be ideal for goldfish - and you can have lots of those! As they stay smaller, they are much better suited to most garden ponds.
Here's a chart that was very eye-opening to me about the difference between fish as they grow:
Koi Length and Weight - Ammonia Produced, and Waste Produced
This chart also lists koi weight by weight and how much ammonia and waste they produce. Koi get heavier as they grow and produce more ammonia and waste.
russellwatergardens.com