you should never use the full dose recomendations on the bottel start about half. if you have only soft corals they will not take up that much calcium. simple water changes will do in some cases. one time i over dosed calcium hydroxide it took 3.5 weeks to come down but did not loose anything . you need to figure out you calcium up take.whene your calcium returns to normal ckeck a couple times a day for 3 or 4 days .if you started at 425 ppm and 3 days later its 400ppm you know you calcium uptake is about 8ppm a day.try to keep your alkilinity on the high side.