I think 6 for the Galaxy/CPD, they are very shy unless they have a bigger school, and 6 seems to be good minimum school number (based on my research and listening to the advice of others), five would work, if one dies which you would still have a school.
Don't know about the other kind. You can double up on the filter pad media to get more BB. Will check out your other thread "rimless"
Cool thanks so the galaxy rasboura is a celestial pearl danio? I've heard danios can me nippers is it true with theese ones. And I'm running 2 sponge filters 1.5" dia x 4" tall sponge.