Is this practical?

[Soul]

To scatter a whole tub of Rhowaphos onto the middle compartment of the sump rather than getting an FR dispensor that has to be pump operated.

[w3ish3ng]

why not get a filter bag? some reefer are running it this way

[flying carpet]

The fine partical will float and will go back to your main tank. How big is your tub? Introducing and removing phosphaste and silicate at one go is not advisable as it may stress your tank inhabitants.

If you decide not to use an fr you should at least use a bag for your rowa.