Setting Up New Saltwater Aquarium

[REBEKAH]

I set up a saltwater aquarium 1 1/2 ago using live sand and rock. After 24 hours I added a damsel fish. The fish has been eating and acting normal until about 2 days ago when it appears to have gotten a fungus infection (cotton like spots on dorsel fin and body). The levels in the aquarium have been consistently normal according to the test strips, I also check the salinity regularly. Can I treat the fungus infection without harming the curing process of the tank? The tank and rock have begun to grow green algae.

 

[WILDER]

How big are the spots sounds like columnaris at the moment, just want to make sure its not whitespot.