phosguard is (IMHO) the only thing I don't recommend for phosphate removal. It's a quick fix, aluminum based phosphate remover. Use it, get it out of there and then go with real GFO.
There has been a huge ongoing debate about phosguard, I had kind of hoped it would just disappear from the market... 1) it leeches aluminum: The only people that say it doesn't leech aluminum into your tank is seachem and the guy behind the counter selling it and 2) it strips the phosphate out of the water too quickly. Nothing should be done fast in this hobby, and dropping phosphate overnight can be as disastrous as raising by a huge amount overnight.
Howeve,r if your tank is new, it may not make much difference, just don't leave the media in there too long. Get some hi-cap from Jerry, it's pretty much established that iron oxide is perfectly safe for the reef system. Aluminum, notsomuch.
Again, just my opinion, however google "phosguard leeching" and I'm sure you'll find a lot of results to read. ROWAphos is a good product, fairly easy to get as well...
**edit oh there's no livestock in the tank? Where did the phosphate come from? Used liverock? Make sure you figure out where your high phosphates are coming from (mine were coming from a rubbermaid bin that was filling my makeup water with phosphates). If it's coming out of the rock, keep using hi-cap until your numbers are 0.00 If it's from something else, you'll keep adding it back in (as I was doing), which can be uber frustrating.
