Blow-off of top cropping yeast

[mgr_stl]

Brewed a Russian imperial stout and used Wyeast English ale III yeast. Aside from that not necessarily being the best choice of yeast, I wanted to see if there would be any fermentation issues due to the blow-off loss.

Being a top cropping yeast, does that mean there's a lot of yeast at the top doing its thing? Or does that term have a different meaning? Did I lose a bunch of active yeast through the blow-off tube?

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[mgr_stl]

How long would you wait before taking a gravity reading on a big beer like this?

 

[DurtyChemist]

Harvest the top cropping yeast.

Take a gravity reading when you see no more activity or when it's slowed down enough to sample. I'd prefer to wait until activity is at a minimum and you're considering racking it to a secondary/keg to store/age it.