I always thought the Albino's and Julii's only got like 2 inches and the Bronze and Green's get a little larger IMO. I love the antics of cories so I am never concerned about the size of them compared to other fish and I would say you could keep 6 without any problems IMO. I have 8 Julii's, 8 Ototo's and 8 LF Albino Bristlenose Plecos in my 4 foot 120 with plans of picking up at least 6 more cories and they get along with everything.