I've seen that product, but haven't used it before. Did you rinse it before putting it in the sump? You might try dialing the skimmer down for a bit, then slowly bring it back up to capacity to see if it still goes crazy.
I have used phosphate removers with no problem with my skimmer. I did use the remover in a Magnum HOT power filter though, and not in a bag in the sump. That may have made the difference.
