Will black and brown Oto's group together?

[LancsRick]

A little while ago I lost a couple of brown Oto's from one of my tanks, so there is just a pair in there. I know they prefer being in groups of 4/6+, so I was going to add some more, but I can only get hold of Black Oto's at the moment. Will they group with the brown's, or will they stay separate?

Cheers!