I just looked up pricing, recommended quantity per gallon and assuming a monthly replacement based on a quick search what most people do, and assuming all other variables are identical, you are paying almost 3x as much for Phosguard than bulk gfo per month to do the same thing. You do not NEED to tumble gfo, you just need to have good flow running thru it, if you use it in a canister filter, I'm sure there is enough flow being forced thru the media to be effective, even thou an inexpensive media reactor like a tlf150 would be a better choice for any filtration media than a canister filter.