Tony, just curious why you are going with Phosban vs Bio-Pellets. I went with pellets, just because I did.....
As far as your flow, do you mean which setting in the MP10? I think that depends on how much flow you want to change. You can play with it a bit and see which you like best. But be careful, depending on how close to the substrate it is, if you have it on a volatile setting, then you can create a sand storm. I actually had my MP40 set too high and it dug a trench in my sandbed right down to the glass.