I have had zosteraes for about a year now, with many breedings. In the zosterae tank I have:
-Many Zoanthids
-(2) sexy shrimp
-cerinth snails (eats red slime)
-pea crab (abandoned by dead flame scallop, eats red slime)
-tiny hermits (zebra (eats red slime) and blue legged)
-nerite snails
-glowing snails
-yellow gorgonia
-purple whip gorgonia
-green star mat polyps
-dwarf pipefish
-different macro algaes
Never had a problem with anything not mixing well. Everything is placed accordingly. The gorgonias are right by the water flow, which keeps it happy and it diffuses the pressure, which keeps the seahorses happy. When the hermits get big enough that they may do harm, I either put them in my other tank or take them to LFS for exchange for tiny ones to replace them.