My pH is 7.8, my parrot feather is yellow and I have one group of
water hyacinth in the pond and they don't look great either. I
haven't tried the potash this year, but it is only good for replacing
potash, and it is my understanding has nothing to do with pH. OK,
I'll try the potash too. As soon as I send this and tear myself away
from the chair.

What is your pH and what kind of filter plants (Not potted.) do you
have that are green and growing? I'm not against trying another plant
as a filter plant, I've just had good luck with water hyacinths most
years, but some years they don't grow in my pond.

Regards,

Hal