I'm just gonna go with 1 blue damsel. The tank was for invertebrates anyway. But still, as I said before, my lfs
has damsels and clowns (all different damsel and clown species)(ocellaris, tomato, skunk, saddle clowns, yellowtail, blue, green, 3 stripe damsels and more) all in the same tank. So if I got a clown and blue damsel from that 1 tank why wouldn't they be fine together? I believe that tank is the "tank bred" fish tank as they are keeping all those different species together.