Do your fish have Ich and you are trying to treat with that product or do you have something growing on live rock that you want dead?
If its Ich, you do not want to use this. It will do nothing for your fish. The only two proven cures are copper or Hyposalinity in a QT. Then, while fish are being treated in that separate tank, you leave your display tank fallow for 6 weeks. That allows the Ich parasites in the tank time to die off due to not having a host to live in/on. You end up with Ich-free fish going back into an Ich-free tank. It will never come back if you quarantine any future fish. Going any other way, the Ich will survive (even though you may not see it on your fish) and it will resurface down the road.
There are lots of articles to read about marine Ich online. It's a good idea to understand how this parasite works, as many people assume their fish is cured when the spots disappear (which is absolutely not the case).