Thanks Dave, I never use chemicals other than to remove the chlorine in the pond water, and then I rarely do that as I feel that a little fresh tap water added into the large volume of water in the pond does not hurt, unless I am adding a whole lot of water then I will use a declor the water, I really try to follow nature when possible and use lots of big sedges for best natural cleaning too. I really like to use the sedges (grasses, rushes, irises, plants with a spear shaped leaf) as they are the very best at cleaning the pond water.
I also think the pond should flow all year round as flowing water best removes the harmful gasses and keeps the water fresher and cleaner. I remove extra summer pumps and just run the main pumps that keep the three ponds connected, flowing the water from the top pond down to the bottom pond, this melts the ice very very quick in the top ponds as the water is always kept at a constant level. If you only have one level in the pond, then the ice takes way longer to melt as the water level falls below the ice, as the water is displaced and turned into thick ice. This does not happen in the top ponds as the water is always at the same level as the ice. Many people wonder why I have so little ice and think I have some naturally warmer protected area, may be somewhat true, but the ice on the path never melts away like the ice on my ponds. I have ice on the walkways all around the pond pretty much that has been there for months and not melted yet, as I can assume that the ground is frozen very very hard this year, especially after the extreme cold temps we had this season. When it is minus 40 below, not much difference between Celsius and Fahrenheit, and no warm spot outside to be found.
Lilguy, go as deep as you are allowed for your zone, some city's dictate what you can do, like here in town, any pond deeper than three feet must be locked with a six foot fence.
If you are going to have big koi, then dig it bigger and deeper. as big as you can go would always be better. Every time I re-dig a new pond, I always say to myself, "that is a really big deep hole, that should be way big enough, then come the plants and big fish and then the pond does not look so big anymore! I would go at the very least, three feet deep, and lots of place for shelves to place plants.
Must run to work now, loved chatting with you all and talk later after work.....