phosban, rowaphos, phospure, pura phoslock are all ferrous oxide and 3 out of the 4 proclaim to be the best or use the best grade ferrous oxide. I use phoslock because its cheaper than phosban and rowaphos. I'd use dr foster and smith phospure if the shipping didn't nullify the cheap price. they all work fine (the data discussed below tested both rowaphos and phosban and found them to perform the same used in equal amounts. phosban comes dry, rowaphos comes moist. rowaphos is darker. performance is the same despite the claims). DONT use aluminum oxide. it is proven to leach into the water and irritate certain corals. you can find the data yourself from the advanced aquarist archives but the link is not allowed here. you can read seachems FAQ on their site for the product and they are wishy washy and dancing around what they KNOW is fact (or they should being what they are to the industry). phosguard is probably fine in a FOWLR