Pet got bad breath?

So, I was in PetSmart the other day scoping out their 75% off holiday toys and found this stuff called Petzlife.  I noticed my dog has had bad breath lately and when I examined her teeth, her back teeth seems do be a little dark in color.  Regular tooth brushing is not working.  The oral care gel was surprising on clearance for around 4.00 so I decided to try this in combination with the brushing.  I found this on amazon.com.  http://www.amazon.com/PetzLife-Oral-Care-Salmon-ounces/dp/B000PICBOA/ref=sr_1_2?ie=UTF8&qid=1327377475&sr=8-2
I will try to keep you updated on how it is working out and YES, it does smell like Salmon!  What do you do for your pet?  Any recommendations?