Remember that substrate sauce has .03ppm of PO4, so it will give you a little boost and help the bacteria to kick off. Probio is just good stuff. I've been doing every other week, but I think every week should do the trick with my feeding habits. If you have any questions about this stuff, reach out to Ken (creator/owner) he's super helpful and always provides great customer support. He's active on R2R if you search PNS Probio. I'm going to dose some Yello Sno here shortly. Just dosed Probio yesterday.