There are two type of phosphate, ortho and meta. Hobbyist test kits only detect ortho.

The test for meta involves boiling samples in sulfuric acid as I recall. Not something that is highly recommended on the hobbyist level. Meta phosphate is the organic phosphates I mentioned in my earlier post on carbon.

I said earlier that phosguard is silicate based. That is incorrect as Matt pointed out. IT IS aluminum based. I had a case of mental gas when I typed that. What am I going to do without Matt around to keep me straight. I guess Larry is going to have to do double duty.

Here is a good article on comparative tests of both types. I should warn you, it's is pretty heavy on analytical chemistry. The good thing is that they ran the tests on laboratory type instruments, not hobbyist test kits, so the results should be more accurate and sensitive than what we are capable of.

http://www.advancedaquarist.com/issu...004/review.htm

Gary