The ricordea and zoa's are nonos in my mind mostly because many types require bright lighting. But if you can find low light types, excellent. SPS, LPS, & Brain corals I have seen mostly require Metal Halides which are bad for most octos. Also many SPS have STRONG, LONG nematocysts (sweeper tentacles) which would be very harmful to the sensitive skin of an octopus. Octopuses are obviously harder to keep, I merely try to look for such an animals best 'comfort zone'.