RTN - Now what?

Mack75 · Mar 20, 2025

I suddenly find myself facing RTN, most likely caused by a combination of high alkalinity and pH (pH probe had lost its calibration and read 8,14 when the actual pH turned out to be 8,4) and very low nutrients. I was in the process of fixing the nutrients issue, and things were starting to look better. Two Seriatopora hystrix are already gone, I think my Stylophora colonies are toast, and a few massive plating Montiporas are shedding tissue. What are my options? I assume just ride it out, maybe a water change or two, anything else?

Johnd651 · Mar 20, 2025

Water changes. I had massive salinity swings due to faulty ato a few weeks ago. Water change every couple days and my tissue necrosis stopped and the coral is coming back.

Hockeypunk1 · Mar 20, 2025

That PH swing wouldn't cause the rtn. In my experience it's usually an alkalinity swing especially when you have very low nutrients. It could also be a bad magnet, heater, or pump that is leaching some sort of heavy metals into your tank.
Seriotopora is one of those easy SPS because they grow very fast, but they are very susceptible to alk swings. You can try breaking off pieces that haven't been affected yet to try to save what you can. You can try water changes but if your water is already too clean that might not help much, but water changes could help if there's a bad magnet or something else polluting your water.

p1u5h13r4m24 · Mar 20, 2025

Those ph numbers are fine. Mine drop to 7.8 somtimes and go up to 8.4. Some of the best sps collectors don’t even pay attention to ph. If your nutrients bottoms out that is most likely your issue. You may not even see the affects of it for a few days. With sps you won’t see the results of a change in tank chemistry for a few days.
Relax make sure your chemistry is in check. Most importantly make sure your nutrients are up. Phos up to .3 will even be fine for sps, but don’t do any fast swings with chemistry. Sps need balance so small moves in the right direction. I don’t think you need a water change if you have low nutrient issues.

Dburr1014 · Mar 20, 2025

Mack75 said:
I suddenly find myself facing RTN, most likely caused by a combination of high alkalinity and pH (pH probe had lost its calibration and read 8,14 when the actual pH turned out to be 8,4) and very low nutrients. I was in the process of fixing the nutrients issue, and things were starting to look better. Two Seriatopora hystrix are already gone, I think my Stylophora colonies are toast, and a few massive plating Montiporas are shedding tissue. What are my options? I assume just ride it out, maybe a water change or two, anything else?

Your on the right track.
Fix water quality and a couple wc is a good move. Water changes bring balance to water quality of your missing anything.
You can lower the light intensity for a few days, it wouldn't hurt and probably help.