is UV bad

i just put a UV sterilizer in my tank and ive heard mixed ideas about these. My tank is fairly new and my yellow tang has black ich. I am trying to cut down on ich and cyano which is blooming large scale in my tank. I have about 23 pounds of LR in my 26 gallon tank and a deltec mce300 filter so as far as water filtration i think i am set. any pros or cons to a uv sterilizer would be helpful

thanks

 

pros: kills bad bacteria in your water

cons: it can also kill the good bacteria too
and it can blind you


that yellow tang is probobly to much for your bioload they usually require like a 75 gallon or so, they are big swimmers i would say the best way to get rid of the ich is to get some smaller fish, tangs are really messy

 

thank you