Canary in the mine - which coral do you use?

[karimwassef]

Do you have a particular coral that's hardy but also acts as an early detector of something being off?

Mine is a hydnophora. It's tough as nails but I can tell by its polyp expansion and surface tightness if something's even a little bit off. It's better than any probe.

What's yours?

[CuzzA]

Purple Stylophora. If I don't see what looks like a bunch of white balls (growth tips) glowing at the top of the colony I know something is wrong. When the tips color up to purple I know growth has stopped and it's time to start investigating my reef. It's one of my original sps corals that has now reached full colony status and has been through every change in my reef. So it's quite hardy, almost impossible to actually kill.

[sublime9182]

My acans. When they don't open their feeders during the day I know somethings wrong.... speaking of the devil....

[toothybugs]

My acans and alveopora. If the flowers aren't open, something is janky.

[ridetheducati]

General reef hygiene
Green Slimer shows daily growth.
Rainbow Mille maintain white axial corallites

Specific markers
Nutrients: Hulk Mille - Orange tips fade when nutrients are too high or low.
Potassium: M. Capricornis - colors dull when potassium is low. Purple Monster slightly fades when potassium is low as well.
Alk: Axial corallites will deform when alkalinity is too high on many acros.

There are a few more markers, but the above are the corals I observe weekly.

[karimwassef]

Thanks!

Ridetheducati- interesting symptom to diagnosis on the potassium and alkalinity. Got pictures to show what it looks like?