IRahmatulla;700338 wrote: How fine is that "marine aquarium sand"?  Is it sugar fine, or oolite?  Sometimes with finer sand, if your powerheads are pushing sand around you will get a lot of particles in the water.  How cloudy is it?  Is it see through, or milky?  Can you tell if it is a lot of tiny bubbles?  What kind of filtration are you using?  If you have overflow/ect, are you using filter socks?  If you are using some form of HOB system, do you have a carbon pad in it?  When you set it up, did you add the sand to the water, or the water to the sand?  Any stirring?  Also, you mention not having a bloom, or whatever.  Maybe the UV light, is letting some form of bacterial bloom in the water column.  I have never experienced this, but I have read.  Did you add your CuC yet?  How long have you been running those lights from the FW tank?  Maybe I am overloading the quetions...