Have you tried asking this in the chemistry forum? I've read a bunch of stuff on here regarding PO4 before, but can't say I've seen this particular question asked. I would think that it wouldn't really be detrimental to anything but algae, but then you go back to the old adage of nothing good happening quickly in a reef tank, and always thought that that applied to changes in chemistry as well. Still, I'd be interested in hearing what the chemistry gurus had to say about it...