Problems with Acropora corals

[Reef_do_piza]

Good morning, my friends—how’s it going? Could someone help me out? I’ve had these Acropora corals for about 2 months, and in the last few days, they’ve started to look like this. They actually grew this way.

HANNA
10/15/2026, Kh 7.8, Po4 0.15 and No3 8.0
Today Kh 7.6, Po4 0.08, No3 7.8

 

[Gumbies R Us]

How does everything else look in your tank?

What does your PAR look like?

Anything that could be bothering them?

Flow of your tank?

What are you using to test?

 

[Reef_do_piza]

How does everything else look in your tank?

What does your PAR look like?

Anything that could be bothering them?

Flow of your tank?

What are you using to test?

I haven’t taken any PAR measurements yet. I have 2 Radion XR30 G4 Pro units, 2 Forfish G2 Pro (Brazil) 110W fixtures, and 2 VorTech MP40s in a 120x70x50 cm (LxWxH) tank. I use Hanna test kits.

 

[painter1982]

What caused your po4 to drop in half? What’s your salinity measurements over time? Looks like Apitasia outbreak going on too.

 

[Reef_do_piza]

What caused your po4 to drop in half? What’s your salinity measurements over time? Looks like Apitasia outbreak going on too.

My nutrient levels have always been near zero; I only recently managed to raise them. I believe the drop in phosphate is due to the fact that I slightly reduced the amount of food I provide—I used to feed twice a week with a mix I put together, consisting of various fish foods, nori, clams, etc.—and I also upgraded to a larger protein skimmer, which is actually oversized for this aquarium. My salinity consistently stays between 1.025 and 1.026, as measured weekly.
Yes, I am having issues with *Aiptasia* (anemones), but I’ll be adding a filefish today to take care of that.

 

[painter1982]

What caused your po4 to drop in half? What’s your salinity measurements over time? Looks like Apitasia outbreak going on too.

My nutrient levels have always been near zero; I only recently managed to raise them. I believe the drop in phosphate is due to the fact that I slightly reduced the amount of food I provide—I used to feed twice a week with a mix I put together, consisting of various fish foods, nori, clams, etc.—and I also upgraded to a larger protein skimmer, which is actually oversized for this aquarium. My salinity consistently stays between 1.025 and 1.026, as measured weekly.
Yes, I am having issues with *Aiptasia* (anemones), but I’ll be adding a filefish today to take care of that.

I think your issue is likely due to parameters fluctuating. Salinity being one of them. Par could play a role too. But I’m no expert, there are some on R2R that will chime in.

 

[Reef_do_piza]

I think your issue is likely due to parameters fluctuating. Salinity being one of them. Par could play a role too. But I’m no expert, there are some on R2R that will chime in.

Could this fluctuation—between 1025 and 1026—be harmful, given how small it is? I’ve always kept it at 1026, but for the past two weeks, it’s been at 1025; it’s possible that my tester (Milwaukee) is out of calibration.

 

[exnisstech]

I would look more into the PO4 fluctuating. That was a pretty fast decrease and SPS often don't appreciate that. They don't seem to mind fast increases too much. I have chronically low N and P in my SPS tank and found dosing ammonium bicarb and sodium phophate works very well and is pretty simple to get the amounts dialed in. I never had any luck trying to use food to raise nutrients. I have a hunch coral reefs experience some slight salinty changes but I could be wrong.

 

[Reef_do_piza]

I would look more into the PO4 fluctuating. That was a pretty fast decrease and SPS often don't appreciate that. They don't seem to mind fast increases too much. I have chronically low N and P in my SPS tank and found dosing ammonium bicarb and sodium phophate works very well and is pretty simple to get the amounts dialed in. I never had any luck trying to use food to raise nutrients. I have a hunch coral reefs experience some slight salinty changes but I could be wrong.

I’ll look into it. I’ve been dosing N and P to raise their levels, but it’s been difficult to keep them under control.

 

[exnisstech]

I've been dosing ammonium bicarb to keep nitrate detectable and a diy phosphate using sodium phosphate. Once dialed in I'm getting very consistent test results and coral are thriving. I chronically low N and P for several years I've had to dose. I moved into another tank 4 months ago and that trend continues so I keep dosing. I used to dose a diy nitrate solution but see much better results from coral and test results are more consistent dosing ammonium vs dosing nitrate.

The tank I'm working with.