What are the advantages/disadvantages of using Carbon in a reef tank?

RC will give you lots of information.

Use good quality carbon as bad quality can leech phosphates.

Don't use too much.

Replace it regulary.

I use one cup for about 5 days every 2-3 weeks.

Clears the water, helps get rid of any toxins secerted by the corals.

Pie

Same. I run carbon for about 5 days every six weeks or so.

I run carbon constantly, changing it every 2 weeks.

when you say "run carbon" are you just placing some in a bag in your sump or are you placing it in filter that actuallt gets water movement through it eg. one of those air driven filters with carbon, common in goldfish tanks??

i place mine between one of the baffles in my sump - so water passes through it - its just not forced through it like a filter