HELP /w 1500 Gallon pond! Overfeeding

We went out of town for 3 days, and the person we hired to take care
of the animals dumped a whole 25 POUNDS of Koi wheatgerm food into my
poor little 1500 gallon pond. 25 POUNDS! MY.. GOD.. how stupid could
you get!
*I was stocking up for the winter.*
Well, now its a day after we've gotten home. There is a layer of food
on the floor of the pond that even dwarfs the ammount of leaves before
we had a skimmer. The water is so incredibly filthy, I cant see to the
bottom in the gravity pond's mechanical filter! Visibility is about 3
inches. The pond water is milky *and seriously.. its like I filled the
tank with milk* white. I cant see the colors on the fish from 3 inches
of water.. I have no quarantine tank, was planning on putting one in
this spring.

The food has clogged the skimmer.. is was completely full. Thank god I
bought that auto-shutoff. Food has nearly stopped the drain pump from
working.. its pulling a measly 450 gph *while it usually pulls about
2500 GPH* The pond aerorator doesnt blow bubbles.. seeing its full of
little particles of FOOD..
the rocks I use to give the fish a hiding place were COVERED.. not a
spot of rock to see.
Like I said, visibility was about 3 inches. I did a 75% water change
*drained half way, filled, half way again, filled.* and dumped 20
ounces of 'Ultimate' pond clear *fish store was out of ammonia lock*
I picked out as much dirt as I could.. *most of it being food*
I dont seem to have lost any fish yet, but I do believe I'm going to
lose them when the Nitrates and Nitrites turn into Ammonia.

I then sterilised the filter pads, heavy, medium, and light.. and
sterilised half the biological filter. *sterilising by boiling the
objects* The sand filter was clogged full of food, so I rinsed it out.



After about 2 hours, I noticed a change in the pond.. the water's
surface has a rainbow-like sheen, and foam occurs at the waterfall.


Please, somebody help!