[damselfish pairing]

hello, i own a 40g fowlr tank with 1 yellow tail damsel,1 sebae clown,1 yellow tang,1 juv anullaris angel and 2 chromis and 1 banggai cardinal

i want to add another yellow tail damsel into the tank so they will pair up...but im afraid that they will kill each other..how do you pair up damsels?

heres a video - 1 chromis that jumped out and 1 cardinal

http://www.youtube.com/watch?v=6DN6ZW4oOTs

[Sea Water ( Iwarna )]

Our Seawater is selling @ $1 per bag about 13litres per bag

Operating hours daily (no off day) 8am to 630pm

is the water fully medicated n can we put in the fish immediately?