Okay, gentlemen, quick course on vaginas (consider this a MuscleMom PSA because I'm getting generally upset there are men out there who will swear off eating pussy because some women who have problems are gonna screw it up for everyone else):
A HEALTHY pussy should NOT smell like FISH, EVER. However, there is a range of what's normal for any woman. She will not smell the same from week to week because body odor (which is really only noticable to our species in the pits and groin) is very strongly affected by hormones. Since a woman's hormones change from day to day it's normal for her to smell differently over the course of a month. A stronger than usual "tangy" odor can be caused by a pH imbalance, a lot of sex will cause that and if she hasn't showered in 24 hours or so. This is totally normal.
For those of you who do not like the smell of a "plain" vagina, I cannot emphasize enough ... don't ask your woman to use scented douch or personal sprays or any of that stuff, that's only setting her up for infections, seriously.
Sick vaginas generally have one of two distinct odors:
1. An unpleasant "fish" odor is usually caused by an infection (commonly bacterial vaginosis), she may or may not have itching or discharge with this.
2. A "yeasty" odor (like raw bread dough), particularly if there's a white discharge and/or itching, is potentially a yeast infection.
BTW, neither of these conditions have ANYTHING to do with STDs, however, you can catch them, carry and spread them since guys don't generally show symptoms. This is the reason why a lot of women get recurrent yeast infections no matter how many times they treat the problem, their s/o won't go to the doctor and get treated because he doesn't have any symptoms.
And while we're on the subject ... don't think the old twigs and berries is odor free!
End PSA