I tired the pokeradar to get me a shiney rose-(BAN ME PLEASE) (I hate that poke). I thought someone on here would trade one for something...Anyways, 14 was my best chain. Then the thing failed to get a response and no grass moved. I was saddened.
When the grass doesn't move, just use the radar again. It continues your chain. It's what I did on my Chansey chain when no "rare" patches showed up.
Unfortunately, that one ended at 25 when the fat-ass cow showed up instead of the fat-ass whore.