Tank Smells a Little Fishy

[LeanneP]

I have noticed off and on that I can smell my tank a little when I walk into the room. I have a 90 gallon that I do a 15 gallon w/c every week and I clean everything quite regularly. One thing I don't do is clean the detritus off the rocks very often so I was wondering if that is why I am getting a bit of a smell. Will running carbon take the smell away?

Leanne