Cloudy tank propblem

I setup a 10 gallon tank for a couple clowns I just got and all was good for a week then in a single day it went from clear to really cloudy. I did a 90% water change and again this morning it was cloudy. All params are great except for the calcium is over 600. I have not added anything that would have raised the calcium that I know of, just food. I have no idea where this calcium is coming from or even if it is the real problem or just a symptom. Any ideas and help would be apreciated. Shaun

 

IO salt. It has been setup for a little over a week just as a QT tank for the clowns. I took the clowns out before doing the change and am using this as a learning experiance.