phosphate questions…help and imput

[Amadod2]

so i checked my phosphates today with my hanna checker and it read 0.15, im trying to get in lower, and just did a water change a week ago, i run a 75g tank with carbon and rowaphos which hasnt been changed in two months.

my question is what is the idea phosphate level and what is the max phosphate level a reef tank can do without seeing coral loss in growth and colour.

also does rowaphos leek back into the system??