in one tank, I have a calico bristlenose that spends a half the time out of view. My other tank has a pair of albino bristlenose, The female is always hanging in the front where the food is dropped. The male hides a lot and when he works eggs in his cave, you only see the tail.
But all in all, they are all peaceful and mind their own business and i see them frequently enough that I dont fret about their whereabouts everytime I look in.