Red plating montipora becoming pale

[CedarReef]

I have a red plating montipora (m. palawanensis?) that has been in this location in my tank for about 6 months and has more than doubled in size.
When I got it it was vibrant red/orange, but over the last month I have noticed it becoming pale, especially in certain spots. I haven't observed any pests, and I dipped all my corals when I got them.
Light intensity hasn't changed, the area receives ~200 PAR max during peak

Currently dosing saturated kalkwasser in ATO, but it has been pretty humid lately so I don't think it's enough to keep up.
Had some warmer weather and tank temp got up to 82dF, but now with the cooling fan it rarely strays above 79dF

I have montipora digitata in the tank which is vibrant and growing well, so much that I must start dosing Ca and kH to keep up. I have BRS 2part that I dose by hand.

There is no skimmer, filter sock or filtration on this system other than live rock and there is quite a bit of algae, however I added cheato to one of the AIO sump chambers on a reverse lighting schedule a 3 weeks ago so the algae has noticeably less. Nitrate and phosphate have consistently tested 0 for a long time. I have 7 fish in the tank and I feed once per day.

Temp: 77.6
Salinity: 1.026
Ca: 420 ppm
Alk: 7 dkH
pH: 8.3
Mg: 1200 ppm
NO3: 0
PO4: 0

With that information, what do you think could be causing the paling on the monti?

 

[tzabor10]

Pale on the edges? Is that growth?
Your Alk is low.

 

[Mr. Mojo Rising]

There seem to be no nutrients, 0-0, you should try to get that up. Alk is low, try to bring it up to at least 7.5, but 8~8.5 is better IMO. Magnesium is a little low.

 

[Dburr1014]

The pale doesn't seem to be growth. It's too sporadic to me.
7 dkh is not a problem. It is on the low end but it is also okay.

I agree that zero no3/po4 may be a problem.
I would try feeding more. Maybe 3 times a day for a few days until you see a reading.
One more note, algae happens in any nutrient readings you get. Sounds like you are dealing with it in a proper way so, IMO, I would up your feedings and see if you get some readings.

 

[CedarReef]

Thanks for the advice. I’ll start feeding more to increase nutrients. I got 6 more turbos today to help combat the algae.

 

[CedarReef]

As the nutrient consumption in my tank has gone up, the feeding and light levels have stayed the same. It seems that the combination of low nutrient levels and high light has led to pale, starved corals.

To feed the tank, I have been thawing out a frozen mussel, blending it up mixed with RO water and feeding that over the course of a week. One mussel in a week is not that much.

The turbos have already reduced the hair algae.

 

[CedarReef]

I have a red montipora digitata that has put on a lot of growth, but as of yesterday I noticed some patches where it looks like the tissue necrotized and sloughed off. Since yesterday, it doesn't seem like it has gotten any worse.

It is the only coral in the tank that has this issue, and I have another monti digi that doesn't have this problem.
I did have an alk swing but I would expect that to affect other corals as well, and I thought digi was pretty tough.

A couple weeks ago I added some peppermint shrimp but I keep them well fed by spot feeding them after the lights go out.

I have noticed a hydroid colony below the damage, could hydroids be a threat to the coral? Another concern could be lack of light; all the damaged parts are in relatively shaded areas

Any ideas what could have caused the damage? Alk swing or shade, or is there a pest to consider?

Another note: I added a few corals to the tank the day before I noticed the damage. One of the corals was an acro that had some tissue loss and sloughing tissue (it looks stable for now). I dipped the corals in coral RX. It was upstream from the coral that is damaged. could it have caused this?

 

[Gumbies R Us]

My recommendation would be to raise your nutrient levels and see how your corals respond to that!

 

[Krux]

There seem to be plenty of nutrients, that tank has a fair bit of hair algae... adding more without removing the algae from the equation will only cause it to proliferate.

 

[CedarReef]

For whatever reason, the color has been restored to the Monti, as well as the Acro in the back. I started dosing Mg weekly to supplement my 2-part dosing system shortly after I made the original post, so I like to credit that with the improvement. However, Mg measured at only 1290ppm a few days ago.

Despite my intentions, I still feed about as much as I always have.

As for the Monti that had tissue loss, I just trimmed off the affected parts and rapidly regrew over the wounds, no worse for wear.