You might get some watercress from the store. It grows easily.

In the summer, it dies back in the heat. You might think about water
celery, it thrives in the summer. Additionaly, water hyacinth. Both grow
well and produce lots of discardable plants...throwing out as green plants
what was brown waste. The root systems catch muck and provide great
bactrial surface.

Jim


"btinternet" wrote in message
...
im thinking of growing watercress as a vegi filter. I have a header pool
on
my main pond which is 10'x3' and 14" deep. I am thinking of growing
watercress in seed trays floating on the surface. What would you use as a
planting medium? I was thinking of mixing 2 parts gravel to 1 part clay
cat
litter. Is this a good idea? My main pond holds 3500 gallons and is home
to
11 koi and 4 goldfish.
thanks
Leigh