Even though the tank is 65 gal
, if it is not at least 4' long to allow for swimming room, a Y. tang would not be recommended. As Melosu said, you need to find the root of the problem, and being a new tank it's not surprising there are some nutrient/algae issues.
I have only been topping off with distilled water
Have you checked it for NO3
? If not I would recommend taking it to a LFS
to test it, if you don't have a PO4
test kit. I assume you have a NO3
already. Those two things are generally the primary fuel source for algae.