the sand stirs up alot when a fish goes near it and blows water with its fins...it silts up and (because it is fine) makes the tank look like a sandstorm....
How long have you had the sand in the tank? What kind of sand do you have? After a while in the tank it should tend to settle faster when a fish or something stirs it up. I myself have 4in. of SD sand and it sometimes stirs, but quickly settles.
