Too much light? Lack of nutrients? Both? Something else?

[Daniel Berazadi]

In my latest post I asked about the health of one of my acroporas as it seemed to have been bitten, it is complitely healed and in fact it si growing a new branch.
The problem is with two of the acro frags that I recently moved to the final position after a few weeks on the center bottom of the tank.
As you see in the picture, when I moved them at the begining of september they started to loose some colour.
I felt it was maybe too much of a light change too sudden so I dimmed the lights slightly ramping them up slowply day by day, and I also placed a mesh on top of the fishguard so that it would filter the light a bit more.
Seems I managed to colour up the bottom one, although a white patch has appeared at the bottom.
But the top one is the one I am most worried about, despite the mesh it has not improved at all.

The anemone is not touching it, I am positive, however today it will be gone.
Also both of them have lost colour, not skin. I have seen RTN and STN, and this does not look like it. The skin is there, is not loosing it, it just... does not have any pigments, or microalgae, no idea.
The worst thing about my tank is the lack of nutrients.
Lately I have been feeding more and adding aminos daily, I have managed to raise NO3 to 2ppm.
However PO4 is still 0 as per my RedSea Test kits (the pro ones).
Just last week I started dosing a tiny bit of PO4 to see if I can get detectable readings.

The tank is almost 3 years old
Volume: 200ish Liters
Temp: 25C
Salinity: 35
Calcium: 480
Magnesium: 1250
Alk: 9.3 (this could also be it, I am in the process of lowering it down, I overestimated my doser)
NO3: 2
PO4:0
Weekly 10%waterchanges.
The light is a tiny RedSea LED 90, and is not even at 100%, which is odd. I was under the impression that acroporas needed much more than what that lamp gives at 100%, yet I am seeing what I think is bleaching? Is it maybe just alkalinity stress? Lack of nutrients? Everything at once?

Should I continue trying to get the nutrients a bit higher, lower alkalinity and just keep pushing forward but leaving the corals were they are? Should I move the corals?

The rest of my corals are perfectly healthy and growing like weeds, is these two that are still a bit iffy.

Thanks in advance so much, you are the best

 

[twentyleagues]

The pic on the left looks like low nutrient high alk. I saw this years ago when the ulns craze started and I jumped on board, but no one said hey guy in ulns you need to lower alk. Mine was always in the 10 range. Could be low nutrient and lighting in the right pic or alk/nutrient ratio. Dont ask what the ratio is I dont know if there is actually is a "ratio" just at higher alk levels higher nutrient levels is better. I found a happy place around 15-20n and .1-.2p at 10+dkh

 

[Dburr1014]

No color at the tips but with flesh means growing, or burnt tips.

You definatly need nutrients. Higher alk;low nutrients is asking for burnt tips.

I always tell people who have zero nutrients and trying to raise them, get a reading on phosphate before nitrate.
This is old school but stills holds today. You might get some algae or Dino going the other way.

Another thing to do would be to lower the light intensity for a few days. Get the readings on the nutrients then ramp back up again.

 

[LARedstickreefer]

It’s your zero phosphates. Dose them until they stabilize through feedings and you’ll probably turn things around.

 

[Pod_01]

As mentioned I would attempt to get the PO4 up. From my experience nothing good happens when PO4 is zero or sinking fast towards zero.

Feed the fish more, use liquid based PO4 (there are diy recipes), use coral foods they generally pack phosphate. Also you could consider Tropic Marin Phos Feed.

Maybe bring the Alk down a bit 8-8.5 range.

Good luck,