Nitrates, Phosphates and Bares...Oh MY

[Nicole8ca]

I have a whole bunch of questions, so I'll try and keep them organized.

I have some brown algea growing.
My nitrates are at 15,
and my phosphates are at 0.5.

I assume this is the reason for my algea. I do a 20-25% water change every week. I don't over feed. My tank is 77 gallons with about 90 lbs live rock.

I have a canister filter with ceramic and foam. Is this where my problem is? Should I take out the foam and add carbon? I'm not going to lie to you all I have no idea what the ceramic does-it came with the filter so I put it in.

I also have a remora protein skimmer and laguana uv sterilizer. I rinse the 'cup' of the protein skimmer every couple of days. Do I need to do a more thorough cleaning of it?

Now with that said I was also looking at taking out my crushed coral sand bed. It seems to be alot easier to vaccuum up waste/junk without it. Will I be opening up a whole new can of problems if I do that?

Any help would be greatly appreciated. Thanks!