Individuals with normal color vision will see a number, while those with a deficiency do not see it. On some plates, a person with normal color vision may see one number, while a person with a deficiency sees a different number.
Your phosphate level should be at or below 100 parts per billion (ppb). If your water chemistry and phosphate levels seem to be in check, one potential cause of the cloudiness in your pool could be dead algae. Phosphates are the food supply for algae, thus high phosphate levels promote algae growth.
When Phosphates are Present, Algae Grows.... Phosphate is the main ingredient in fertilizer. Phosphate is plant food, and algae are plants. If you have had persistant trouble with algae, every year - and it always seems to come back, you may have a phosphate problem in your pool.