Adding a fuge?

[ReefHoboBum]

I have a 150gal that's been running for years so of course it's completely cycled with live stock. I recently cleared it and and reaquascaped and now starting to add more livestock. But I would like to add a deep sandbed in my overflow, which is 24" tall. I was thinking I'd fill it up 6-8 inches worth of sand. How would doing this impact the rest of my tank chemistry as it is? What should I watch out for and what are your thoughts about the benefits/usefulness of this "fuge"?

TIA

 

[ReefHoboBum]

btw, the reason for the fuge is that i would like to decrease my nitrates.

 

[bertoni]

Unless the overflow is very large, I don't think adding sand to it will make a difference.