They can although by how much I don't know, and I'm not sure how many for a tank that size. I've been looking for those myself but I haven't looked up how much per gallon.
I bought 2 yesterday, so I'll see how they get on. I was advised to have 2 for a 55 UK gall tank - apparently they are good at reducing phosphates in planted tanks, which in turn help keep algae down a little more.