Corals dying and not sure why

[keithw283]

So to preface this, I started writing this up and when I was getting all of my parameters I noticed my temps are at 81.5 degrees. I normally run at 78-79. My heater seems to have stuck on and around the 3rd I see an increase in temp. Now I'm not sure if that is the problem so I'm still gonna finish this and see what you guys think.

Hello all, all of my corals that I purchased about a month or 2 ago are slowly dying on me (well quickly at this point) and I'm not sure exactly what my issue is. I have a 240G mixed reef that has been running since May of 2025. Surprisingly, the montiporas were the first to go, then the acros and now my hammers are on the way out too. The zoas are the only ones unaffected by whatever is going on. Even my duncans and Candy Cane didn't make it. My Par is ~350 at the highest peak and ~120 at the sand bed. The acros all sat anywhere between 280-350, the montis were ~220 and the hammers were mostly in the sand bed at ~120 minus the one you see in the pic below. The candy cane and duncans were also in the sand bed.

Parameters are as follows
PH 7.9-8.1
Temp 81.4
Salinity 1.026
Alk 8.42
CA 459
MG 1346
N ~ 2
P ~ 0.01

Another odd thing I've noticed, is that I haven't had to dose anything for a few weeks now and all of these parameters have been fairly stable which is odd to me. I got an ICP test done and it was pretty consistent with my trident acm. There were also no harmful metals or anything out of the ordinary found. N and P are checked with salifert and were double checked at my LFS. Before I started writing this my two biggest concerns were flow or my Regal Angel. I have never personally seen the Regal nip at corals but as we all know, that doesn't mean anything. As for flow, It's an 8' tank with an Mp40 and a maxspect gyre xf350 on one side and another Mp40 on the other side. All set to 50%. With the hammers, duncan and candy cane not doing well, I am not suspecting flow to be the issue. Now my concerns are the Regal or the 81.4 degrees. What do you guys think?

 

[Mr. Mojo Rising]

Are you sure on the par level? Or how long is your peak? Your rocks don't look like one year old rocks to me.
The nutrients seem very low to me, corals do need some nutrients.
The temp might be an issue but being only 2 degrees away from your normal I'm a bit skeptical.
Could be the fish I guess, I'm not familiar with them.
Thats all the idea's I have, hope others can offer help, good luck.

 

[keithw283]

Are you sure on the par level? Or how long is your peak? Your rocks don't look like one year old rocks to me.
The nutrients seem very low to me, corals do need some nutrients.
The temp might be an issue but being only 2 degrees away from your normal I'm a bit skeptical.
Could be the fish I guess, I'm not familiar with them.
Thats all the idea's I have, hope others can offer help, good luck.

I used an Apogee MQ 210 for the par. Not sure if that's a good one or not but that's what I used lol. Peak is 7 hours. I started a build thread on this tank so you can check that to confirm dates. I did have a pretty nasty algae problem awhile back so that's probably why they don't look as old. Corraline never really had a chance to take hold. It still won't grow much on the rocks. just the front wall of the tank.

 

[EnterName]

It's "funny" because your parameters nearly match an experiment from Rosset et al., 2017 almost perfectly. They exposed corals to 2.36ppm NO₃ and 0.017ppm PO₄, which caused those corals to bleach after 6 months.

Compared to natural coral reef levels, 2ppm NO₃ is insanely high. The high nitrogen availability causes the zooxanthellae to split and reproduce very fast, but then they lack the required phosphate, which isn't too high compared to natural levels with 0.017ppm. This resulted in a low symbiont density and the corals basically starved, even though the nutrient levels could be considered "elevated" compared to natural reefs. (Nalley et al., 2023)

In most reef tanks people keep much higher phosphate levels, which apparently fixes this issue. At approx. 0.03ppm (I'd recommend going a bit higher for safety) the ratio between nitrogen and phosphorus didn't seem to matter that much anymore, so I can only recommend using a DIY phosphate solution to solve the issue. Randy's nutrient target ranges are also much higher, you might want to increase nitrate after phosphate as well.

 

[Peer.Boerner]

Following along to learn. Really hope you figure it out! Hang in there.

 

[Subsea]

It's "funny" because your parameters nearly match an experiment from Rosset et al., 2017 almost perfectly. They exposed corals to 2.36ppm NO₃ and 0.017ppm PO₄, which caused those corals to bleach after 6 months.

Compared to natural coral reef levels, 2ppm NO₃ is insanely high. The high nitrogen availability causes the zooxanthellae to split and reproduce very fast, but then they lack the required phosphate, which isn't too high compared to natural levels with 0.017ppm. This resulted in a low symbiont density and the corals basically starved, even though the nutrient levels could be considered "elevated" compared to natural reefs. (Nalley et al., 2023)

In most reef tanks people keep much higher phosphate levels, which apparently fixes this issue. At approx. 0.03ppm (I'd recommend going a bit higher for safety) the ratio between nitrogen and phosphorus didn't seem to matter that much anymore, so I can only recommend using a DIY phosphate solution to solve the issue. Randy's nutrient target ranges are also much higher, you might want to increase nitrate after phosphate as well.

I agree that nutrients (PO4 & NO3) are too low.

“Compared to natural coral reef levels, 2ppm NO₃ is insanely high.“

Inorganic nutrients do not fuel coral growth on wild reefs:
POC & DOC fuel growth.

 

[EnterName]

It's "funny" because your parameters nearly match an experiment from Rosset et al., 2017 almost perfectly. They exposed corals to 2.36ppm NO₃ and 0.017ppm PO₄, which caused those corals to bleach after 6 months.

Compared to natural coral reef levels, 2ppm NO₃ is insanely high. The high nitrogen availability causes the zooxanthellae to split and reproduce very fast, but then they lack the required phosphate, which isn't too high compared to natural levels with 0.017ppm. This resulted in a low symbiont density and the corals basically starved, even though the nutrient levels could be considered "elevated" compared to natural reefs. (Nalley et al., 2023)

In most reef tanks people keep much higher phosphate levels, which apparently fixes this issue. At approx. 0.03ppm (I'd recommend going a bit higher for safety) the ratio between nitrogen and phosphorus didn't seem to matter that much anymore, so I can only recommend using a DIY phosphate solution to solve the issue. Randy's nutrient target ranges are also much higher, you might want to increase nitrate after phosphate as well.

I agree that nutrients (PO4 & NO3) are too low.

“Compared to natural coral reef levels, 2ppm NO₃ is insanely high.“

Inorganic nutrients do not fuel coral growth on wild reefs:
POC & DOC fuel growth.

Not sure what was wrong with my statement?

I'm not saying it's better to keep tanks at natural nitrate levels and didn't mention coral growth.
The phenomenon of zooxanthellae starving of phosphate depletion at usually considered "high" phosphate levels when nitrate is too elevated is well documented: https://www.sciencedirect.com/science/article/abs/pii/S0048969722061927?via=ihub
At a certain threshold the N:P ratio no longer seems to matter regarding this phenomenon or at least the target ranges of Randy are safe even if they match ratios that were previously shown to be deadly when nutrient levels were overall lower.

 

[Subsea]

“Not sure what was wrong with my statement? “

Who said something was wrong with your statement?

I choose to emphasize how wild reefs differ from most captive reef tanks. In my 35 year display: ammonia, nitrate & phosphate all show zero ppm. While I do dose ammonia for insurance, I rely on in tank food webs to process nutrients into micro fauna & fana to feed hungry mouths.

Inorganic nutrients do not fuel coral growth on wild reefs: POC & DOC fuel growth using the “microbial loop”.

 

[EnterName]

“Not sure what was wrong with my statement? “

Who said something was wrong with your statement?

I choose to emphasize how wild reefs differ from most captive reef tanks. In my 35 year display: ammonia, nitrate & phosphate all show zero ppm. While I do dose ammonia for insurance, I rely on in tank food webs to process nutrients into micro fauna & fana to feed hungry mouths.

Inorganic nutrients do not fuel coral growth on wild reefs: POC & DOC fuel growth using the “microbial loop”.

Ah okay, sorry then I just misunderstood your statement. My bad that's on me
Thanks for explaining! I always respect your opinion and thought you knew something I had missed.

 

[keithw283]

Thanks for all the replies guys! I'm gonna start by trying to increase phosphate. Can somebody link me to a different product for a diy recipe? It seems like that one is out of stock on Amazon. I don't mind getting neophos but I want to diy a lot of my dosing on this tank as it is going to get pricey on a tank this size.

 

[Fish Fan]

Thanks for all the replies guys! I'm gonna start by trying to increase phosphate. Can somebody link me to a different product for a diy recipe? It seems like that one is out of stock on Amazon. I don't mind getting neophos but I want to diy a lot of my dosing on this tank as it is going to get pricey on a tank this size.

https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/

 

[keithw283]

https://www.reef2reef.com/threads/diy-phosphate-dosing-recipe.1109919/

Thank you. And if anybody is curious. It was my Jaeger heater that stuck on. I got a finnex heater controller from brs as a freebie and I also have a hydros. I have 2 heaters. One heater was plugged into the finnex which is plugged into the hydros controller. The Jaeger was plugged directly into a standard outlet and ended up sticking on. Whoops. Everything is back to normal on the temp side of things.