Kole Tang and Purple Tang...together in 65g?????

[Skimmerking]

There is lots of ways to get rid of that crap.
First have a refugium set aside to export tha nutrients in the main tank.

Or get a sea hare (Bad idea when all the algea is gone it will die).

Do more water changes hoping to expel the nutrients. Or get a algae blenny small fish tha will graze on the rock for ya.
Or a phosban reactor to help out too.

a purple tang and a kole tang are 2 of the agressive ones out there in tangs