You need a mechanical filter to trap the suspended algae before it gets
to your bog. I use a rubbermaid container with a snap-on lid. Drill
holes in the sides, place your submersible pump in, and stuff the box
full of polyester quilt batting (cheap, effective, and you can rinse it
with a hose and re-use it). Drill a hole in the lid of the box for
your pump outlet. You may have to clean it every day or two until the
algae is under control. The bog will act as a biological filter, and
the plants in the bog will use up a lot of nutrients that the algae
needs to grow. I like water cress because its so fast growing. Pick
up a bunch or two at the grocery store, poke the stems down into the
gravel and in no time at all it will put out roots and grow like crazy.
You'll see a major difference in your water quality.

Ann in Houston wrote:
Hope y'all don't mind, I've posted the same basic content under a
couple of
different threads, in hopes of increasing my chanes of getting an
answer.
We finally built a gravel bog to filter the pond. We just finished
it,
yesterday. It's visibly making a difference, but it has a lot of
catch-up
to perform, and of course, we have lots of powdery looking algae
trapped on
the surfaces of the gravel. Will it continue to scrub the algae from
the
water, even if it has a ton of stuff already trapped, or do I need to
do
anything to help it get up to speed, and into the maintenance stage.
Can we
leave it alone, and just let the natural "bugs" do their thing over
time?
How does the decomposing trapped algae figure into the build up of
bacteria?
Is that part of it?

I'm thinking maybe I should
1. add the sludge-eating stuff to break down the trapped algae?
2. put some mesh over the nozzle of our shop vac and suck the
initial
overload out?

Which should I do? Some combination of the above?
Any advice would be appreciated.