Dirty sand bed. How can I clean it up?

[BCReefer]

Over the past few months my sand bed seems to be getting darker, like there it is dirty. It is hard to explain. When I look at other websites I always see a nice clean sand bed. I only have about 4 – 5 small blue legged hermitts and 10 snails which I thought would be enough?? I am not the biggest fan of the hermitts as they can be aggressive from my experience.

I usually check my parameters every month and I have not noticed anything wrong other than my calcium is becoming lower quicker.

My Bak Pak was out of commision for about 2 weeks and my water was getting a little green so I have increase the water changes and fixed the skimmer. My water is clearer but the sand is still a little dark.

Any suggestions? I tried taking pictures but they don’t really show what I am talking about.

I am using coraline crushed corals for my sand bed and it is about 1.5 to 2” deep.

Thanks
Patrick