I can't seem to get any foam/froth floating, even after 24 hours of brewing. I have 3 bubblers in the reservoir, should be more then enough? My dry ingredients are in a thin material silk screen type bag, It keeps floating to the top of my reservoir, should i throw a rock in the bag to weigh it down, will that help? I just want frothy/bubbly floaty good stuff, but its not happening. Thanks