Did you get the water tested? I am not sure of how you go from soil to water for conversion purposes but the water will generally reflect the soil. Having said that read below. You appear to have high calcium so see the [ ] part below. Here is the fact sheet link.
http://srac.tamu.edu/index.cfm?catid=25 see:
SRAC 460 Control of Clay Turbidity in Ponds
Although not nearly as effective
as alum, gypsum also can be used
to control turbidity but without
the loss of alkalinity. Gypsum
must be added to achieve a concentration
of 100 to 300 mg/L for
effective turbidity control. For
most ponds, gypsum application
rates will range from about 1,000
to 2,000 pounds per acre (Fig. 4).
[ In hard-water ponds (calcium
hardness greater than 50 mg/L),
the water is nearly saturated with
calcium and gypsum may be ineffective.
In that situation, alum will
be the only effective coagulant.]
All the coagulants mentioned can
remove phosphorus from water.
As phosphorus is an essential
plant nutrient, it may be necessary
to fertilize the pond after treating
it for turbidity.