[Lupin]

Welcome.:wave:

What about nitrites? If your nitrates are zero, your tank may not have cycled. As for the sick chromis, I'm guessing you failed to quarantine the new arrival which is often considered as a carrier of diseases regardless of whether the symptoms are visible or not.

 

[Lupin]

Aren't clownfish just as territorial as other damsels?:question: And in a 20 gallons, fights will break out frequently.

 

[Lupin]

Can I save the sick chromis?

Try to post a picture of your chromis. Pictures often help.