FishFrik has a good point.. a refugium is an excellent way to provide nutrient export.
You CAN do macros in your main tank, but as he said if you are not vigilent in pruning and keeping a careful eye, they can do more harm then good. It's not an overnight thing, but most macros do root in the rock, and the slightest piece to survive can grow back.
Also, they can go sexual, fouling the water.
Also, if they die off, whatever bad stuff they consumed can get right back into the water.
In a refugium they are pretty much contained, but still require regular maintenance.
Transfering filter media in fw is the same as cultivating bacteria via LR die off or shrimp cycling in sw. In years gone by, the preferred method in sw was to use damsels or the like to seed the tank with bacteria because they are/were considered expendable.
This site promotes humane cycling methods, altho many LFS still say to use the fish cycling method.
I say it's your tank, do as you wish (not like I can stop you heh).
You'll get alot more compassion around here if you have some however, so pick wisely I suppose
I don't know the specifics behind the bacteria, but I do know they are not the same critters. SW is SW, FW is FW..same principle however.
(You could take previously established live rock or sand or filter media from a sw tank and use it in a new tank to have an 'instant cycle' if you moved things properly)