I am not sure what your situation is but here is some info.

The recommended
pH range for aquaculture
is 6.5 to 9.0 (Figure 1).
Fish and other vertebrates have an
average blood pH of 7.4. A desirable
range for pond water pH
would be close to that of fish
blood (i.e., 7.0 to 8.0). Fish may become
stressed and die if the pH
drops below 5 (e.g., acidic runoff)
or rises above 10.
Pond pH varies throughout the
day due to respiration and photosynthesis.

You could try to get the stuff out by scooping it out with a plastic tub with holes in the bottom to let the water out. Get it in the tub put on the top on and drag it out slowly to let the water seep out.