You will see me use this picture from Bush Gardens in Florida often. It has a lot of good points in it.
The Good Points:
This is an example of a decent Koi pond. It is deep enough having a depth of over 4 feet. There is a quick drop off in depth at the shoreline, giving little or no access to raccoons and Herons. The pond is buffered by a ring of plantings close to the pond limiting access. Areas that are accessible to people, have a short fence or rail. The plantings are at hedge height but still low enough see over and take pictures. The walkways are paved , stepping stones, gravel, or are decked. It has a place for birds that is protected (the overhanging log). Bush Gardens has dedicated almost half of the grounds to bird habitat.
The Bad Points:
It has a place for birds that is protected ( the overhanging log). This log will an provide excellent place for a King Fisher to sit and pick off your 4 to 7 inch fish. What saves the Koi predattion in this pond is the cloudy water, and the depth of this pond. The only real protection (cover) for the Koi is the cloudy water and some over hanging decking. Remember green water is not always bad. The birds sitting on the log are fish eaters.
There is a water quality problem in this pond. The level of nitrogen is very high. My guess is there is a tremendous amount of waste generated by numerous Koi and birds. The Algae is feeding on there abundant fertilizer produced by the critters and converted by the bacteria in the pond.
Suggested Cure:
Since there are large Koi in this pond and not very much cover for them and the emphasis of this park is to showcase birds.. Doing nothing may be the best suggestion.
Other wise the following is suggested:
1) Provide more cover for the Koi. If we clear up the water the birds will eat them.
2) Set up a 3 section sediment/bio-filtration system3stage
3) Create a bog area at the edge of the pond, not in the pond proper, to run the out flow of the filtration system to remove the usable fertilizer produced by the Bio-filter.
4) Increase the dissolved oxygen in the water by aeration , water fountain, or with a waterfall
Thanks to Bush Gardens Florida!
Mark Paulsen
Scenic Harbor Nursery
Scenic Harbor Nursery