fish scratching against rocks, parasites?

[seaduck]

I just added a yellow clown gobie to join my catalina goby. Both fish are scraping against the rocks in a manner which seems to be trying to scrape off parasites or something. I have corals in the tank. Is it time to add a uv sterilizer? any other options besides removing the fish?

 

[Triggerfish]

carefully look at both fish for evidence of whitespots..