You could try H202, hydrogen peroxide, as a last resort.
Google and read up on it first.
I have not personally tried this method, just reading up on it.
Here is a start
http://www.nano-reef.com/topic/26870...s-to-prove-it/
http://www.frozenocean.org/t1710-hai...rogen-peroxide
http://www.reef2reef.com/forums/reef...fing-tool.html