I think the difference is the polyps on a pokerstar stay green no matter if it's in the center or on new where there is new growth. Rainbows seem to have more of a variant with splattering of red on the new growth edges.
Ken-Good stuff. I have your old eheim you can use once i switch tanks over. I say two vortechs or tunze on opposite corners and sides. Seemed to work for my tank. Maxijet mods would work if your trying to save some dinero.
I was planning on using it to help keep my rock work suspended so that flow could go beneath my rock work. This should help reduce detritus buildup,which seems to be a problem when going bare bottom