Unknown coral please ID

[Karin]

It can be very difficult to tell Porites and Montipora apart, particularly when you aren't in the ocean where you can pick up clues from the environment.

Montipora is in the same family (Acroporidae) as those nice branching Acropora corals and other members of the family Poritidae look nothing like the encrusting Porites you probably have here: Goniopora and Alveopora, for example.

If you want to tell Montipora and Porities apart you can't rely on color or tentacles or growth form or any easy clues like that, although Porites usually lack the elaborate papillae and tuberculae (warty growths ) that Montipora often have.

The only way sure to tell is by studying the tiny, round hole called the corallite that is the skeleton of an individual polyp. Hundreds or thousands of these cover your coral; polyps may extend from them at night or even during the day in aquaria. These corallites hold the key to identification.

Inside each round corralite are little dividing walls called septa. (Some corals also have little walls that come out of the holes called costae and walls that go in AND out called septo-costae…). But back to those septa.

The septa often go in cycles - two short, one long – that type of thing. And the family Porites has a unique septal plan. If you look really closely it can look like a wagon wheel but you practically need a magnifying glass.

I’m new to this group (what fun!) and need to find out what AI is. But here’s my guess. You either have a Porites lichen or a Porites asteroides. P. lichen is common as dirt but not found west of Mexico so if it came from over that way forget P. lichen.

P. lichen is a dominant species in lagoons or reef slopes and is usually yellowish-green to brown. It has irregular and variable septal structures. It’s found all over the Indo-Pacific and looks a lot like what I can tell from your picture.

P. asteroides often has a lumpy surface once it gets big and tentacles are often extended during the day. It’s usually bright yellow to dull gray-brown or sometimes greenish, but that’s in the wild (I know nothing about tanks). Its common in all reef environments all over the world including Florida and the Caribbean. P. asteroids also looks a lot like P. branneri, with very neatly spaced corallites. If your coral ends up being really blue or purple you might have one of those, but they’re more rare.

Whatever you have, enjoy it because its very cool and a nice surprise!