Jeff,

You don't have to have the Baq at any particular level to start converting, but the lower the Baq, the shorter the conversion time. However, during the conversion, the more you keep your chlorine up, the shorter the conversion, as well.

Post #4 in this thread is a basic conversion by an AG pool owner...
http://www.poolforum.com/pf2/showthread.php?t=3703

Basically what you want to do is to get your chlorine up to 12-15 ppm (cal hypo is fine) and keep it there until the Baq is used up and the chlorine levels are holding overnight. This is best (and quickest) accomplished by testing and adding more chlorine to get back up to the 12-15 multiple times daily. The pool will turn some weird colors during the conversion, but you'll see some progress being made when it goes to cloudy blue. You'll need to leave your filter running 24/7 and brush the pool daily during the conversion, and watch your filter pressure--backwashing is frequently as the Baq is broken down. Keep in mind that AG filters are often under-sized, so once the pool goes blue/cloudy, it make still take a few days to get it clear. Once your chlorine is holding without losing more than 2 ppm overnight, then you need to change your filter media and begin balancing your water. How long this takes depends on how consistent you are about maintaining the high chlorine levels--for some on the forum, it's taken a week. For some, it's been done over a weekend.

Hope this helps!!

Janet