My LMB must be allergic to Hair Algae, but he has taken to Rod's food...
LOL...I have a sea hare and he is starting to make a dent after about 3 days. It's the only thing that has worked for me other than tweezers!. You will have to find the cause and you already said you suspect phosphates so just add some phosban. The problem with sea hares and turbos is that they will wreak havoc in a frag tank by knocking eveything over that is not glued down. You may just try moving your frags into your display + phosban + lights out until gone. I would think this the best solution as long as you elimate the cause it should not come back.