Who Gives A Fish Forums

18 inches is right on the edge where actinics start mattering more. If you're dosing amino acids, that could help too. My SPS started coloring up way better after adding them.

Actinic lighting's great for fluorescence, but Zoanthids need a bit more white spectrum to really thrive. Try bumping the white channel to 30% and see if they respond. Also, how old are your bulbs? Actinics lose intensity over time, even if they still look bright to us.

Sounds like your kerbs are gettin' ready to spawn, that's why the male's bein' so protective of the castle, keepin' other fish at bay.