pulsating corals

Question
Hi,
 I have had my 25 gallon aquarium for over a year now and since this is my first aquarium I am learning as I go. When I first started my aquarium my step son set it up for me, he has an aquarium business in Florida, I started with live rock and pulsating corals, crabs and snails, no fish. Everything was going fine, no problems at all for the first 8 months. I went to our local aquarium store and purchased some blue and orange mushrooms and a tree leather coral to liven up the tank. I then purchased a couple of clown fish after that. Everything was going fine for a couple of months and then the pulsating corals started to shrivel up and eventually die. Same thing happened to my tree leather. I talked to my step son and he asked me if I was doing my water changes and filter cleaning which I was doing. I would like to purchase some pulsating corals but I would like to know what caused them to die. My mushrooms are doing alight, not as good as they were doing but they are still alive. I check my water status weekly and everything is right where it should be. My calcium is a little low but it is still in the safe range. Any suggestions would be appreciated.

Answer
Hi Glenn,

    A common problem seems to be nitrate buildup. The tank cycles as it should over the course of several months and then it's very possible to have a nitrate overload. This will not be harmful to fish or inverts but will kill most corals. Are you adding trace elements to the water? You can buy trace elements as an additive which will be beneficial to the corals. There is also an invert food you can purchase that will add sustenance to the water. Also, what type of lighting do you have? Some corals can live for months and suddenly deteriorate if lighting is not right. Please get back to me and let me know what you find.

                                   thanks, Gerry.