Grapefruit addition to a Hefe?

I have a Bavarian in primary right now and have been thinking about trying something new by giving it a grapefruit undertone (so you don’t have to put fruit in it). Does anyone have experience with fruit additives? Not sure whether to use the zest which I feel may be too bitter, or how much of the fruit to use for a 5 gallon brew. Thanks for the help!

too bad you already brewed it, you could have used hops to get the grapefruit flavor.

for some unknown reason I keep getting grapefruit tartness to all the beers I have brewed. You want yours in, I can’t get mine out. Go figure. Just as speed said, certain hop additions will give you that. Maybe even fermenting warmer(low to mid 70’s) may even do it for you. I just bought a freezer to use with an external temp control. Hope the lower temperatures will clear out that darn tartness.