That's the reason to start dosing vodka. It takes the nutrients that the HA needs for survival. Vodka is a slow process, though. It can take a few months for it to ramp up to the level needed.
I've been dosing for a month to help get rid of HA. If you want a quicker solution, look into AlgaeFix Marine. There's a good thread about it in the Chem. forum. I'm on my third dose of that, too.
A few changes I've also made to help;
-Rinse frozen food
-New Bulbs
-Better Skimmer
-Cut back lighting
-Cut back feeding
-Purchase a Sea hare
I've finally gotten ahead of it I think. I returned the sea hare last week as the food supply was getting low. I still have some limited growth but nowhere near the tufts of grass I had on the rocks before.
Good luck