Koi Pond Undercrowding

Good job! Ideally, your success would be best if you had less than an inch of fish per ten gallons of pond water. That means that for a 1,500 gallon pond, you would have the best possible luck by stocking 150 inches of fish or less. That would be, for example; ten fish, of a fifteen inch length each.

At that rate, most filtration systems will generate satisfactory results and your pond water change regimens will be satisfactory.