corals and anemones
Depends upon the anemone. Many will wander around your tank creating havoc with your corals (particularly hard corals).
There are a couple of exceptions (generally):
1. Sand anemones remain small and if place in a conducive spot (under good light with their base buried in the sand next to a rock) will stay put. I have kept dozens of these over the years and only have one 'migrant'. Be aware, however, that these anemones will not be adopted by clownfish - at least none of mine have! These anemones are easy to keep.
2. The anemone H. Magnifica (aka Ritteri) can also be kept with corals if one is clever in setting up the tank. Although this anemone is generally considered to be 'delicate' and hard to keep, my experiences have been positive. Since these animals love light and current, I have kept them from wandering by setting up a tall rock (like a pedestal) at one end of my 6 ft long tank away from the coral section. Thus, the anemone must retreat from the light in order to get to the corals - this it has never done! This anmeone will be accepted by most clownfish.
One other point: it has been my experience that in the stress of shipping H. Magnifica ofter expells its symbiotic algae and may be quite pale when first put into the tank. It is therefore important to feed it for the first few months until it can regenerate its algae.