Here's an interesting tidbit... not only is phosphorus taken into algae as they grow, it also precipitates chemically where calcite precipitates on the outside of algal mats. Don't take my word for it, read all about it at http://swamp.ag.ohio-state.edu/current%20research/water%20colume%20productiv ity.html Peggy Murdock - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For SC email list T-and-C, send: GET TERMS-AND-CONDITIONS.CURRENT to [log in to unmask]