I haven't tried kitty litter, but would be concerned about the mess
generated when the koi tip over the pots. Coconut fiber would be
lighter. Coconut fiber is available in:
* bricks (expand to a nice loose fluffy medium when you add water. I
toss mine into a large plastic bag, bucket or wheelbarrow first.) -or-
* chunks (these are commonly used for potting orchids. Just fill half
of pot with chunks, then top with large, 3 inch or more, "koi-proof"
flat river rock; soak planted pot before putting into pond).

I converted almost all of my pond plants to red lava rock (recycled from
two 55gal filter barrels!) covered with flat river rock two years ago.
The plants do well and the koi don't root in them as much. Now, if the
raccoons would not tip over the pots on the ledge, everything would be
fine. Will be tying the pots to the pond rim this year to try to foil
the happy little critters!
--
Kathy B (Oregon -- sniff, no snow here)
3500g pond w/ 13 pond pigs
2 sun worshipping pharaoh hounds,
and one "koi detective" lhasa apso
("don't bother me now, I gotta
keep an eye on those koi")

Lee Brouillet wrote:
It seems that the general consensus of this group, when asked about
soil-less planting media, is to go the "well washed kitty litter" route.

it was also suggested that I try coconut fiber, as it was lighter.

Which is better, and why?

Also, in doing a search for coconut fiber, it
appears to be available in little blocks, like you would use for planting
seeds. But how would you repot a lily, with already established roots? ...