calcuim bentonite

I bought some calcium bentonite yesterday.
I have green water in my pond and it won't clear.
Its been up and running since March.
15x15 4ft deep.
About 9 Koi of various sizes, none bigger than 13 inchs.
It has 3 bottomdrains witch goes into a 4x10 4ft settlement/filter pond.
My pump is a Sequence External Self Priming Series 1500 - 5400 G.P.H 1/3 HP
The out take is a Venturi into the pond. I do have a small pipe also that
leads into a small veggie filter.
Water test shows.
Nitrite 0
Ammonia is 0
PH is between 7.0 and 7.5
I have a good bit of water lettuce and hyancits but no lillies.
I don't think lillies will grow that deep in water.
I live on the coast of Ga. and bird predators are many here.
My previous pond even with netting on the predator birds would stand on
plant shelves and pick out my fish.
So with this pond I didn't make shelves and haven't had any problems with
predators. But now its green water.
It gets really hot here also. My set up is just like a friend of mine and
his pond is crystal clear and he has a lot more Koi. Alot bigger also.
The only difference is he has no trees in his yard and I do.
Should I let the pond be and wait it out? Seems like water would clear by
now though.
Or use the calcium bentonite and if I do, how do I use it?
Thanks,
Priss