Clear water does not always mean healthy water. I have to admit that, although my water looks clear in my photos, there are bits that one can when one gets right on top of the water and looks down into it. I do use a bog garden to filter my water, which I feel goes a long way to clear healthy water for my koi - but I also do not have a bottom drain.
Loretta - what I am wondering is what type of planting medium do you pot your waterlilies in? I know that many people use the clay unscented kitty litter and this will attract the koi to root into the pots as they love clay. Truthfully the only time I have had a problem with my koi rooting into my pots is when I tried the tropical waterlilies. The koi have not bothered the hardy water lilies. I came to the conclusion that the tropical waterlilies must taste better to the koi than the hardy water lilies.
What is your plan to keep your water clear of particulates? What type of filtration do you use?
