well thanks guys, i have had problems with the yellows, they are so mean. All the others are fine and never seem to bother each other. I started off with the large unicorn tang and a purple from my other tank, then added 7 yellows all at one time. Had a battle with ich right after, lost 2 tangs then ich went away.
I added a sailfin, no problems, and the naso, no problems. Then the last change was 1 powder blue and 3 convicts all the same day.
I think adding in groups helps, and also dont mix anything with yellows that have the same body shape as the yellow's.
The sailfin and covicts are apparently just different enough that the yellows didnt mess with them when added.
I wont ever be able to add a black tang or a scopas or another purple as I know they will be killed.
So with tangs its tough but I am lucky I think and they are my favorites in the tank right now.
As for the aquascape, I did a couple mounds trying to keep a lot of free space for fish to swim and corals to fill up over time
Chris