i have been adding a calcium and alkalinity supplement to my 37 gallon reef tank (following the directions on the bottle) and everything was looking good, then two of my fish died in one day and my coral began to look like crap. i tested my water and the only thing that was wrong was my calcium was at 550 ppm. can the calcium be the cause of the deaths and the reason for my corals looking bad. should i buy a different test kit?

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.