Hi, I have 5 Corydoras (last 5 in shop) , they have been in my tank for about 4 weeks now. 2 of them are doing something strange , they lean on each other side by side , "shoulder to shoulder" it looks like they are trying to push each other sideways , they then tip back vertically head up and then swim backwards togther. Are they just shoaling or are they "getting friendly". They are only about anm inch long , if that. Any correspondace greatly appreciated.... 
