What does burning corals mean?

[MolaMola]

Didn't want to hijack a tank journal, but what does it mean when you say something burned corals? Do we see bleaching? Do they turn pale, white, then tissue disappears?
Can burning be caused by Alk/Ca dosing when solutions touch the tissue? Can it be caused by light?
I might have this going on with some corals in a frag tank. It has cubic orbit LED lighting but is only 12" deep. Also, students hand dose 2-part in front of a circ pump.

 

[Ibn]

Burnt tips are usually caused by high alk and low nutrients level. Bleaching of corals is different since there could be a variety of causes, but it's mostly from a stressor of some sort. That could be high light, coming from a low light environment and not properly acclimated, temp spikes, etc. Zooanthellae are expelled which causes the coral to lighten up and if all are expelled then you get an overall white coral, that is susceptible to algae.

I haven't had any issues with 2-part dosing in front of circulation pumps before. I did that with the ecotech pumps and with the gyres since it's the quickest way to get the additives distributed into the tank. Some of the sps are basted by 2-part at times.

Burnt tips on PC rainbow. Overall colors aren't affect. The tips are burnt, where tissue recedes and are sites for algae to gain a foothold.

Slightly bleached setosa. Overall colors are affected and not as deep/dark as it should be. Caused by low nutrients.

The Zeovit method is another time when you will see very light colors, which is caused by additives which causes the coral to expel some of their zooanthellae.

 

[MolaMola]

Very helpful @Ibn ! The burnt tips photo looks exactly like my hydnophora. At first I thought something was nibbling on the ends. And I think some chalices are looking like the setosa but paler. Thanks!

 

[tankguy]

I always learn something from Ibn