adding more Yellow Zoster Butterfles

[marinelife]

I have 2 Yellow Pyramid Butterflies (Yellow Zoster Butterfly) and want to add more.
Do these like odd numbers or does it matter? I also have a black Pyramid Butterfliy (black Zoster Butterfly)
I was thinking of 3 more yellows but wondering if the Black would play a roll in the numbers.

Thoughts?

 

[revhtree]

Moving to fish discussion.