what causes fish / corals to die?

[feegus]

Is natural really not possible? Can fish have heart attacks? Strokes? aneurysms? Blood clots to the gills? All these causes would present as sudden deaths...if fish can die from these things.

Hi, is there any way to rule out things such as heart attacks? Considering its occurring to multiple fish could it be a bad supplier? I cant see obvious signs such as quick breathing or marks, until of course they disappear or cannot swim and then die soon later. usually they stop eating the night before and I do not see them the next morning. In the future when this occurs do you think putting them in a seperate tank would be beneficial - or would it be too late? I appreciate your thorough help.

 

[Jenny_rs]

Do you have a refractometer? It is the best way to measure the amount of salt in your tank. You should be monitoring this as it should be kept around 1.023-1.026. When doing water changes the new water should be the same temperature and salinity as the tank water. In my experience (and with many others as well), not keeping this stable can cause stress on your corals and fish. There are too many variables to pinpoint what the issue is, but you should be keeping an eye on your salinity, ph, kh, Calc, mag, phosphates, nitrites and nitrates at minimum. Some even test for iodine and strontium as well. Temperature also should be around 78 Fahrenheit. I have also been having issues keeping my corals happy but I attribute my problem to too high nitrates despite having a skimmer and macro algae. Best advice I can give is to do more research.