Dwarf angels can be very aggressive. I'd recommend getting one only. If you get 2 be sure they are as different as possible and introduce at the same time. I have a flame angel that is about 2" and it is the bossiest fish in the tank (120 gallon with about 10 fish), plus it occasionally nips coral and once destroyed a large toadstool in a week, ripping a large piece of the stem, so the cap totally detached and took over a month to recover. It has since calmed down and is not a problem now.I've had success keeping multiple species together but they are quarantined together to reduce the risk of aggression and get tehm used to each other. Once a dwarf angel is established in a display tank trying to add any more is not likely to be successful. Behavior issues may develop as the fish mature as you are likely going to get subadults and as always an aquarist needs to be ready to rehome any fish at any time.