Coral Browning, should I be concerned?

[ReefsandGeeks]

I recently performed some maintanance on my tank and have noticed that my coral polyps on many of my coral are browning. In particular, a cactus coral I have seems to have brown growing up from the base but still colored it's normal green around the top 1/2-3/4" from all of the tips. I'm not sure if I should be concerned, or what action I should take to make sure the coral recover.

A couple days ago I did a 30 gallon water change on my 150 gallon tank. At the same time, I added a bag of GFO and a bag of carbon to the sump. Just prior to the water change, I lightly scrubbed some of the live rock with a toothbrush. 2 days before the water change, I dosed the magnesium portion of my 2 part as I had gotten to the end of my 2 part gallons.

I checked my water parameters, which are below.

Alk: 6.5 dKh
Ca: 380ppm
Mag: 1300ppm
Ammonia: 0ppm
Nitrite: 0ppm
Nitrate: ~0ppm (API test kit only goes down to 5ppm, but looks like 0)
Phosphate: 0.05ppm
Salinity: 37ppt (I am working on lowering this slowly. currently at 36ppt)


I'm not sure what would be causing the browning of the coral. The water looks more clear after the water change, and my glass is not getting dirty as fast. My lighting is the same and feeding is the same.

My initial thought was adding GFO, which has needed changed out for quite some time, probably dropped the phosphate too fast, but I'm not sure that would cause the coral to brown? I thought that would make them bleach if anything. Maybe the carbon did something?

Any direction would be appriciated. Everything I've looked up that I thought may have changed doesn't seem to cause browning.

 

[MondoBongo]

is it possible to see any before and after pics?

color change in corals can happen for a lot of reasons. usually when i see browning, my first suspect is too low of light levels. if that's not an issue, then nutrients can also be a culprit.

the correlation with adding new GFO and a color change might be more than just coincidence. too low of nutrients can also negatively impact coral color. looks like you tend to run a pretty clean tank.

when my tank i'm in now was new, i migrated over a lot of my SPS to it. they were extremely pale for the first months to a year, until my nutrient levels started climbing up.

today my nutrients are too high, as evidenced by all the algae, but when they were too low i absolutely did see a change of color.

 

[ReefsandGeeks]

Sure, this is my first response with Tapatalk, so I'll see if I can get pictures to attach correctly...

Sent from my SM-N950U using Tapatalk

 

[ReefsandGeeks]

lighting hasn't changed, but I can bump it up to see if it helps. is browning possibly caused by too low of nutrients? I could try feeding more, or dosing less carbon (vinegar) and see if I can bring it up a bit. I currently feed 2 whole small shrimp and a scoop of pellets every day. I have 2 tangs, a 6" porcupine puffer, a 3" trigger, pair of clowns, and a blenny. The puffer eats the shrimp, and the other fish eat the pellets and whatever mess the puffer made by chewing up the shrimp.

 

[ReefsandGeeks]

I don't have any recent before pictures to attach. As you can see from the pictures, the polyps on most of the coral are browning, but not so much the flesh. On the cactus, the flesh is browning. Zoas in the tank seem to have normal color as well as a hammer coral. A couple of birds nest coral maybe have marginal browning, but noting noticeable.

 

[ReefsandGeeks]

Interesting find, see next post for details

Sent from my SM-N950U using Tapatalk

 

[ReefsandGeeks]

So when looking closer at my cactus coral, which was the only coral that had significant browning, I noticed that it looked great from the water surface, but through the glass it looked brown. Long story short-the coral was just knocked over and tilted back some which exposed the underside of the coral, which is much browner as it doesn't get any direct light. After re-positioning the coral, it looks much better

I forgot that I haven't glued this coral, or a few others down, as i wanted to rearrange a few of them that have just been sitting loose for a few months while I decided where they should go. Either a fish or urchin bumped the coral, and it just happened to tilt just enough that it wasn't obvious, but also enough to make it look bad.

I do still have some browning of the polyps of other coral, but they are not bad enough to cause immediate concern. So I'll slowly increase the lighting over a few weeks and see how it affects the coloration. Otherwise, I'll keep feeding and nutrient export the same so I only change one parameter at once since I don't feel there's any urgent issue threatening the coral. I'll post some pics after a few weeks to see how they have colored up (hopefully).