rust colored sand
 

I have a light layer and heavery areas of a brownish /rust color on my sandbed and on some rocks I think its cyno ??? any book or web site pics anyone can suggest and how do I get rid of it? a water change was just done a couple days ago and water tests show ok .

Sounds like diatoms to me.

Could be diatoms, too.

I know we had a problem with cyno we were told it was from over feeding by everyone and we weren't. One of the guys at big al's aquariums disscused everything to do with our tank and after a hour of showing position of rocks ,type of fish ,all the chemicals ,corals ,filteration ,he said it was due to not enough circulation in the tank

ok since I have limited the light for a few days it has decreased quite abit there is still some there but there is a big difference so what would it be now (cynano or diatoms )after no light for the last few days??????

It's not a new tank and I also cut down on some feeding

so any idea please so I have a better idea what I should treat for?