I brewed a chocolate stout (OG: 1.066, yeast: WLP001) about 10 days ago and at this point aerobic fermentation has passed and most of the yeast has gone to the bottom but there is still some floating on the top and it hasn't changed for days. it seems like there if a lot of "surface tension" on the top keeping it from sinking. anything i should do? or should i just try to avoid it if it doesn't sink by bottling time?