I use both Red Spike (GRACILARIA TIKVAHIAE) and Thick Ogo (RED GRACILARIA) in my Display Tank.
The only problem is that my tangs eat the Ogo faster than it grows, so I wouldn't recommend it for nutrient export if you have Tangs.
The Red Spike, on the other hand, gets left alone completely. I have read that the same is true for Dragon's Tongue (HALYMENIA DILATATA). There are also several species of calcareous macros that fish will avoid completely.
The only challenge with Red Spike or Dragon's Tongue is keeping it anchored down. I ended up using Superglue to tack it onto some of my rock work. I tried simply wedging it underneath rocks or trapping it between two rocks, but with my gyres it always seems to be a matter of time before it got loose and started drifting around the tank.
You can leave it free floating if you don't have a lot of water flow or if you have "dead spots" in your aquascape where there isn't a lot of flow.
From a nutrient export perspective, the "red" species of macros won't take up as much as Chaeto would (for example), but it does help.
Bottom line - there is nothing wrong with putting Macros in your display!
