Blue Moscow ragged tail

[Nanaof4]

0 ammonia, 0 nitrite, 5 ppm nitrates, 6.8 ph, 78 degrees, all male tank, his tail wasn't as big as the other Blue, but now it's all ragged and looks to have holes? New to the hobby. 3 months in and this is my first issue to speak of. Any thoughts are appreciated.  

[Scapexghost]

Looks like fin rot to me. If you have a qt tank, put in in their and slowly raise the salinity to 15 ppm. If not, treat the tank with a antibacterial, like maracyn. Long term, try to raise the pH to at least 7-7.2

[Nanaof4]

Thanks. Dumb question, what test should I look for for the salinity? When you say slow, over the course of a few days, a week? Which antibiotics work best? Sure hope I can catch the little stinker! Thanks again.  

Is it contagious and will the fin repair and grow back? 

[Colu]

What you can is a course of kanaplex in food feeding a small amount twice a day for 7 days as most cases of fin rot are caused by gram negative bacteria or you can quarantine and treat with Aquarium salt 1 table for 2 gallons just remember to only add the amount of salt back in that you take out so if you do a two gallon water change put 1 table spoon of salt back in