I had it happen in my tank once where i had an algae bloom that started out cloudy like this. I checked my water parameters cuz i thought it was an ammonia spike but everything was normal. the next day my water was greenish and 2 days later you couldnt see what was in the tank from all the green. Have you checked your water parameters? Or recently did a water change and rinsed filter media with tap water. I had an ammonia spike one time when I washed the filter media with tap water (one of my doh! moments) and the water didnt have an odor that i noticed to it.