Low gravity blow-off?

[sundog14]

Using 6.5 gallon glass carboys for 5 gallon batches, I've never had a blow-off at < 1.065. However, I have a Hefeweizen (1.052) that decided to go blow-off after ~ 20 hours. I used one pack of Wyeast 3068 and 2 grams of Fermaid K. The only real difference of this batch versus others is that I used O2 for the first time...about 30 seconds?
Any thoughts? Too much O2?

 

[m00ps]

Hefe yeast are notorious for large krausens, along with a few other strains

 

[Crispyvelo]

The only brew I had explode in the fermenter was a Bavarian Hef, though it was in a bucket, not a 6.5 carboy. Keep an eye on it or you'll have a mad lady at home

 

[sundog14]

OK, thanks for the replies.
Now I know......