Help - green algae out of control!

OK, so I've already reduced the photoperiod of my tank to around 8
hours a day (night lamps on the rest of the time)...and as those
who've read my stuff before know, this is a relatively new tank (I
think its about 2 months running now). The only animal type stuff in
the tank are about 8 turbo snails, 6 hermit crabs, and one lil' ol
clownfish (plus a small coral piece). The issue that I'm having is
that the algae growth seems to be absolutely out of control, coating
the overflow box, and walls of the tank with thick, green, hairy
algae. I've added phosphate remover in a sack to the sump, at the
recommendation of my LFS...but am somewhat at a loss as to what else
can be done. Is it, perhaps, time to add some kind of grazer, i.e. a
yellow tang? This stuff is growing UNBELIEVABLY quickly...I scrubbed
the tank sides last night, and came down this morning to new growth
springing up all over. The live rock seems to be kept pretty clean,
but it seems like the stuff is growing MUCH faster than anything the
snails can keep up with...

Thoughts?
Mitch