why no white corals?

[Randy Holmes-Farley Verified Community Expert]

There are actually some naturally pale/white corals that are zooxanthellate--Cycloseris, Pleuractis granulosa, and Sinuorota hexagonalis being a few of them.
Cycloseris sp.; Guam | Credit: Marisa Agarwal

Pleuractis granulosa; Egypt | Credit: Ingo Rogalla

cf Sinuorota hexagonalis; Kwajalein Atoll | Credit: Scott & Jeanette Johnson

Except for the brown parts, some of those corals do not look healthy to me, but perhaps they are just among those corals with low zoox levels.

 

[thamnasteroid]

Except for the brown parts, some of those corals do not look healthy to me, but perhaps they are just among those corals with low zoox levels.

The corals are not bleached, as they aren't highlighter white. There are pigments which make corals pale, although they are unknown. P. granulosa is almost always pale/cream-colored, and Cycloseris has a white color morph. We just aren't used to pale/white corals, as they are not often imported in the hobby.

 

[Randy Holmes-Farley Verified Community Expert]

The corals are not bleached, as they aren't highlighter white. There are pigments which make corals pale, although they are unknown. P. granulosa is almost always pale/cream-colored, and Cycloseris has a white color morph. We just aren't used to pale/white corals, as they are not often imported in the hobby.

That may be true. Cream colored corals are often fine. My fox coral grew rapidly and was cream colored.

But I’m not convinced corals in those photos are in good shape.

 

[thamnasteroid]

That may be true. Cream colored corals are often fine. My fox coral grew rapidly and was cream colored.

But I’m not convinced corals in those photos are in good shape.

I've seen enough photos of these species to know that they are fine. Generally, you would see skeleton or dying flesh if they weren't in good shape. It seems that pale corals are more common in inter-reef habitats with sandy bottoms and more sediment.

P. granulosa are virtually always pale, and the only Sinuorota specimens (not many; these are rare) I have seen are pale.
White is a pretty common color in Cycloseris:
https://www.inaturalist.org/observations/208248654https://www.inaturalist.org/observations/203325530https://www.inaturalist.org/observations/204136620https://www.inaturalist.org/observations/197229932https://www.inaturalist.org/observations/197216949https://www.inaturalist.org/observations/195222590https://www.inaturalist.org/observations/179258781https://www.inaturalist.org/observations/179258718https://www.inaturalist.org/observations/164376320https://www.inaturalist.org/observations/164069979https://www.inaturalist.org/observations/163806430https://www.inaturalist.org/observations/163806425https://www.inaturalist.org/observations/163723261https://www.inaturalist.org/observations/153213160https://www.inaturalist.org/observations/151970956https://www.inaturalist.org/observations/150105805https://www.inaturalist.org/observations/148793487https://www.inaturalist.org/observations/147180105

 

[Randy Holmes-Farley Verified Community Expert]

I certainly accept cream colored corals as being healthy. I’ve had many myself. Bubble corals, for example. They just are not white. Maybe that is taking the original question too literally, but to me, this is a white coral:

https://www.coastalconservationleague.org/blog/deep-sea-corals-biology/
Large reef building stony coral, known as Lophelia pertusa, are naturally white!

 

[Seansea]

Lazy daisy pipe organ coral. Straight up white polyps. Mine had some green in it. Died after a year mysteriously. Think I had it in too low a flow area and they like alot. Super cool looking tho in a tank of crazy colors stood out.

 

[i cant think]

with all the coral colors that are out there, and different types. why is there no white coral?
and when I say white, I'm talking healthy coral that is meant to be white.
you can find every color of the rainbow, but that one.

unless there is white coral out there, but I've never seen any

Ice-Fire Acropora echinata is somewhat white.

 

[Naekuh]

The Original PomPom Xenia is white, and its pretty as heck, and it pulses on top.

But it will probably drive you crazy on how fast they spread, and how difficult it is to get off.

 

[thamnasteroid]

I certainly accept cream colored corals as being healthy. I’ve had many myself. Bubble corals, for example. They just are not white.

We are just not used to seeing pale but healthy corals, as we don't see them in the hobby. Sometimes, corals are pale or have brighter colors because they rely on feeding for a higher percentage of their energy needs, so they have less zooxanthellae in their flesh. I'll ask some coral biologists and get back to this.

 

[thamnasteroid]

@Randy Holmes-Farley Okay, I asked Joe Rowlett about this. I was wrong about white in corals being caused by a pigment; apparently, it's more of "the absence of darker pigments and a reduced density of zooxanthellae." Joe mentioned that pale/white corals "tend to occur in silty habitats," likely because more suspended food means less zooxanthellae is needed for energy production.

 

[Formulator]

Just to address the obvious problem with white: to be photosynthetic one needs to absorb light.

To be pure white you cannot absorb light. Hence lack of white plants and other photosynthetic organisms.

Some may be quite pale and have a lot less ability to photosynthesize than others, but still need to be off white.

There certainly are colorless and white NPS (nonphotosynthetic) corals. I had some come in on my live rock.

Can’t believe it took so long to state the obvious… This is the answer.