Jon. Most all test kits just test for Inorganic P. as Nikki mentioned Saliferts kit is very reliable. When using it you have to take this statement into concideration. "when you test for P with a IP test kit and get a level ready on it, It is telling you that your tank is so saturated with organic Phosphates that they can not bind any more and thus Inorganic P is still available".
On the P sponges, again as NIkki said thier are two types ferric oxide and alluminium oxide. Alot of folks have posted problems when using the alluminium based ones. the problems are with bad and/or negative effects with thier soft corals. In the realm of products made with ferric oxide, thier are several brands on the market. The two most popular brands are rowaphos and phosban. they way they work is that x ammount of media will remove Y amount of IP for z amount of water. In a scientific test it was shown that Rowas product removed 5 times more IP from a set ammount of water then did Phosban, so keep that kind of stuff in mind when purchasing.
Hope it helps.
Mike
On the P sponges, again as NIkki said thier are two types ferric oxide and alluminium oxide. Alot of folks have posted problems when using the alluminium based ones. the problems are with bad and/or negative effects with thier soft corals. In the realm of products made with ferric oxide, thier are several brands on the market. The two most popular brands are rowaphos and phosban. they way they work is that x ammount of media will remove Y amount of IP for z amount of water. In a scientific test it was shown that Rowas product removed 5 times more IP from a set ammount of water then did Phosban, so keep that kind of stuff in mind when purchasing.
Hope it helps.
Mike