I've kept a tiny bit of chaeto in my sump area (it hasnt grown in months), but I understand it is frowned upon as it can hold detritus and, when more dense, turn into a mechanical filter. Just what I've read.
I was wondering about putting a powerhead in my sump to push water to an elevated container with rock and then just let gravity take the water back to the sump. Or use an Aquaclear HOB filter on the sump, with some rock in it.
To add to what Spanky said, if your tank is low nutreant enough, Macro should not grow. The other thing is that macro tends to trap deatris for it's own use, this keeps it from the skimmer and removal. I think you would be taking a step backwords.
I use one on my BB to help lower the Nitrates it helps a little if I get lazy on water changes and I trim and clean it often not really sure it is helping that much though water changes are the best for lowering Nitrates and getting detritus out.
Well, my idea was to take some of the rock out of the tank so I can have a more open aquascape. It is not too crowded but I figure I could put some rock on a refugium since my sump wont hold much of it. I did not think about the algie not growing because of lack of nutrients but now I see.