Starki + Multiple Damsels?

[blaxsun]

I have an Azure Damsel and three other Blue Devil Damsels that get along great - but I also found a really nice mature Starki Damsel (probably 2”) that would make a great addition. Is one more damsel (or another blue and yellow one) a recipe for disaster? I can pass on the Starki - just the first time I’ve seen one in a few years.

 

[JumboShrimp]

What size tank (gal./length)? Lots of rocks?