Filtration

hey everyone. ive been working on my pumps and filtration methods. i used
to pump about 8 gallons a minute through a somewhat thick filter material
and within a week my pond was pretty clear. at the time the filtered water
went directly into the pond from the filter material. now, i have about
10-15 gallons per minute cascading down a waterfall and the top is filled
with hyacinth. there is no filter material now... when i use filter
material (even with the old set up) i was cleaning the material almost
everyday. i havnt had to change it all now with the hyacinth as my filters,
but the pond is completely green now. what should i be doing in order to not
be cleaning my filters everyday and get my pond back to being clean. The
filer is about 1 foot off the bottom of the pond so it doesnt pick up any
muck.. is this correct? any help is appreciated
thanx!
John