Floating plants and current

I'm finding that the water in the lower two barrels of my pond is too
turbulent for small floating plants. The water lettuce seems to ride
its way to a quiet spot against a marginal and stay, but the azolla gets
pushed under at the spillway outflow and tumbled around underwater.
Then its roots fall off and clog up the filters. I've finally netted
most of it out of the lower barrels, except for some that's more or less
"corraled" with black airline tubing because the fish need the shade.
Not exactly elegant.

Even worse, I learned that azolla fixes nitrogen. I now suspect that
the nitrogen fueling my green water is from decaying bits of azolla
roots everywhere - I had a nitrate source and didn't even know it.

I wanted lilies but don't know to tell whether conditions are OK for
them in the lower two barrels. Flow is about 200gph through the
spillways connecting the three half barrels, with the spillways ending
about 2" above the water surface for light but not excessive splash.
From watching azolla and submerged plants, the current tends to flow
down from the spillways, up on the far side of the barrel, and splits to
flow back towards the spillway around the sides. I tried to set the
ball valve at the lowest setting where all the debris (currently
Cambomba leaves and azolla roots) ends up in the bottom barrel with the
filter. The top barrel is different because it has the pump outflow at
the bottom so the surface is less disturbed.

Can anyone take a guess about lilies or suggest other large floating
plants that are tolerant of this sort of current to shade the pond? And
legal in California - I can't find water hyacinth and only got water
lettuce through a friend. Or do I have too much current?

Thanks so much...again!

--
__ Elaine T __
__' http://eethomp.com/fish.html '__
rec.aquaria.* FAQ http://faq.thekrib.com