No worry about the BB. They will expand depending on the amount of ammonia and nitrite rather than nitrate. They will not die out completely. That doesn't mean they are ready at all times if you were to suddenly double/triple the bio load by adding a boatload of fish, though.
I find dosing seperate dry ferts works much better for me as I can change as the tank shows I need. With liquids we get to buy a lot of really expensive water and often pay to have it shipped!