The water clarity will change depending on water temp, available sunlight, and wave action or lack of it. Clarity here will bounce from 24" to 96" depending on the time of year and amount of plants growing in the pond.
Up here, we don't usually have to fertilize, only *maybe* once to get a bloom going. Also, if you are feeding your fish, that is a form of fertilizer, so I wouldn't be that concerned about adding it if you were feeding heavily.
There is a difference between a bloom and turbidity due to suspended particles. A bloom is the bottom of the food pyramid in a pond, turbidity cuts off the bottom of that food pyramid. Also, in ponds with very clear water, there isn't much there food wise for YOY fish to get a good jump start on life.
I try to shoot for 24" to 36" visibility with a secchi disk, I start to get nervous when it starts to drop below 18", especially if the pond doesn't have aeration.