My sand bed in my 75 gal tank was such a nice white color a couple of weeks ago. Now it has this reddish/brown color over the top of it. What is this from? and how can i fix it?
I just replaced my sand bed because it had planaria on it. It is about 4 weeks old. I don't really know what to call it, but it isn't stringy or anything it is just on the sand bed.
