Cloudy Water

There may be something spawning in your tank.

 

Is there a color to the cloud?

 

Here's an article about the different colors of the cloudiness. The fact that it goes away after the lights come on is baffling. I've not have cloudiness in saltwater, but have had it in freshwater. The color indicates the cause and will then indicate what should be done to cure it.
http://saltaquarium.about.com/od/aquariummaintenancecare/a/aa_cloudywater.htm

 

I don't remember what kind of snails I had once but they made my water completely white. I did have alot of them, at the time. Didn't hurt anything but it was very concerning for a bit.

 

I would check the parameters to see if anything is out of check for a FOWLR tank, then probably do a water change as a preventive measure to make sure it don't get worse.
Thats just where I would start

 

It's been several years and I don't remember for sure but I think it was either Trocus or Astrea. They all spewed out whiteish stuff at the same time but it was only for a little while and not several days. I've also had bristle worms do a similar thing.

The snails you put in were pretty tiny so I kindof doubt it would be that.