I agree 100 percent. It's a shame as I really like the diadema.Gorgeous set up!!
The Heckels look a little intimidated, may need to do some rearranging of fish if they don't settle in, jmho.
I know. I plan on removing them this weekend and putting them in another tank. They are much better today after removing their spawn. I bought some time.Fantastic aquascaping, the diadema are ruining it for the other fish though