I like a challenge but even this has me perplexed :rollface:

. . . The thought about TOC/DOC is interesting though. However, if that is the case, why are some people able to cut out water changes entirely and not suffer similar effects? . . .

Well, for one how long are we talking about, a few years, a few decades? What's the success rate at 5 years, 10 years, 20 years?(1) One of the interesting things research is showing is the DOC from corals promotes autotrophic microbial processes which helps maintain healthy conditions for corals. But as time goes by without water changes unhealthy types of DOC and associated microbial processes are going to start building up. Skill is certainly needed to maintain systems for years and decades but there's a whole lot going on in our systems and we've only scratched the surface.

Here's a paper that looks at excess labile carbon and it's association with reef degradation. https://www.ncbi.nlm.nih.gov/pubmed/28895945
And here's one looking at antagonistic interactions of coral associated bacteria https://www.researchgate.net/public...ssociated_bacteria_Environ_Microbiol_12_28-39

One intriguing expereiment are two mesocosms set up in London to study spawning in 4 species of acros: http://onlinelibrary.wiley.com/doi/10.1002/ece3.3538/full They started with gravid colonies which spawned soon after introduction and were able to get them to spawn simultaneously with wild colonies a year later. Since this is an ongoing and tightly controlled experiment with benchmarks it will be fascinating to see what happens over time.

. . . Also, has anyone heard anything about the possibility of corals outcompeting other corals for nutrients as they grow in size? Given that I have several types of large SPS that are still growing will, could this be a possibility? Zoas, blastos, and softies seem uneffected, even my leptos are doing fine.

Sadly there's very little research I've found. To use a gardening analogy, If I plant a bunch of different species together but use just one mainteneance regime most if not all the plants will certainly sprout but as they grow the individual species will have different requirements, not meeting their individual requirements will mean after a while some thrive, some will decline and die.
This paper looked at just 3 species, Porites compressa, Montipora capitata and Pocillopora damicornis. The researchers found the requirements for growth differed for each one. Meeting the needs of one would necessitate the other two would not do as well.

And this paper, https://www.advancedaquarist.com/2008/3/aafeature1, looked at how 10 different acros and montis looked and grew under different color temps. What one species liked another grew poorly under. If we keep a coral under less than ideal conditions how many years should we expect it to live?

(1) And are they actually going as long as they say, locally one aquarist liked to say he went years without a water change when he had never gone more than two, less if you add the water he had to replace for skimming [1/2 gallon a week in a 200 gallon system is at least 10% a year.]
 
Organics in the water column are going to vary a great deal depending on the species in the tank, and likely the growing conditions. I wouldn't take cross-tank comparisons very seriously.

It's possible that corals might be competing for nutrients, but that should be solvable with a bit more food.
 
I got my Triton results back. Just to recap the problems in my tank before I sent out the Triton water samples. Tank 18 months old. SPS corals having RTN and STN. Overwhelmed with red hair algae and cyano starting ...

Salinity = 34 ppt
Ph = 7.80-8.20
Alkalinity = 8.3 - 8.6
Calcium = 420-430
Magn (Mg) = 1230-1260

Here are the Triton results. I see a few values out of their recommended ranges, but I feel like it is not really pointing to the critical problem. I think I can see more with my eyes (algae and cyano bloom). Or can you see any critical problems in the results?
 

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If it were me, I'd try running some carbon and see what it gets you. This is the reason that my latest build is strictly LPS and SPS with no softies. I've read too many stories of toxin releasing softies and I've also never had luck with a mixed reef like that. It's anecdotal, but a lot is in this hobby.
 
If it were me, I'd try running some carbon and see what it gets you. This is the reason that my latest build is strictly LPS and SPS with no softies. I've read too many stories of toxin releasing softies and I've also never had luck with a mixed reef like that. It's anecdotal, but a lot is in this hobby.

Ok, this might also be anecdotal, but it got the worst, when I added 2 Apex WAV to increase the flow. The softies looked pretty upset. So the SPS might have gotten worse due to the flow change or the softies release toxins OR none of the above.
 
To the OP. My approach would be a 100% water change or as close to it as possible. I'm starting to do this to eliminate any buildup / inbalance issues (once or twice a year). I have a 40 breeder as well so it's not a huge deal and cost is reasonable.
Other things I would do:
Check equipment for rust and stray voltage.
Check ro/di for 0 tds
Slowly lower alk a bit
Reduce photoperiod for a while
 
I'd be careful about large water changes. They can cause die-off in the rock, which can in a few cases involve a very large amount of ammonia being dumped into the water column. A series of 20% with the same amount of water would be equivalent to about a 70% change, which should be more than enough to see whether there's an issue, with less risk.
 
I should have said closer to a 70% water change since I have not drained the tank or sump. As long as the alkalinity, temp and salinity are in line with the tanks parameter, I do not see how it can be detrimental. However, I do see how this approach may not be for everyone.
 
If it were me, I'd try running some carbon and see what it gets you. This is the reason that my latest build is strictly LPS and SPS with no softies. I've read too many stories of toxin releasing softies and I've also never had luck with a mixed reef like that. It's anecdotal, but a lot is in this hobby.

I'm starting to think the same. After numerous water changes, backing off of carbon, GAC, Vibrant, and replacing mechanical filtration I've seen no results. Battling off some green algae on the back glass now with GFO and increased organic carbon dosing. All major values have been within the acceptable ranges. Even tried lowering Alk to the high 7's. Nothing has brought back the SPS.
 
You might try to raise your alk a bit. 8dKH is low compared to the amount of N and P you have. My N and P are at 2ppm and 0.01ppm and I have my alk around 8.5dKH. If yours was my tank, I would keep alk around 10dKH. When you have higher nutrients, it is better to raise dKH as well.

Exactly why it is like this, we dont know. But there is a well represented correlation that shows high nutrient tanks are healthy at high alk while low nutrient tanks are healthy at low alk (by healthy here I mainly mean SPS health). There was a thread that I cant find right now that listed the N, P, alk and Ca levels of tanks from a number of "successful" tanks. The coloration between nutrients and Alk/Ca was clear as day light.

I likely explanation is if you give corals lots of N and P to built soft tissue, you also better give them more carbonate and calcium to built more skeleton as well. If not, they dont have enough demand for N and P since rate at which new soft tissue is produced gets limited by how fast new skeleton can be built, this causes N and P to accumulate within the tissue and either cause the corals to brown or bleach. And in vice verse, if you dont give corals N and P to built soft tissue, dont give them excess amounts of carbonate and calcium. This causes them to waste energy trying to maintain lower internal concentration of carbonate and alk, which causes stress.

Since the problems you observe mainly center around SPS corals, an alk issue makes sense even more.

Also when your SPS die, do they bleach or necrose starting from the tips or from the base, or do regions that get more light bleach/die first?
 
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You might try to raise your alk a bit. 8dKH is low compared to the amount of N and P you have. My N and P are at 2ppm and 0.01ppm and I have my alk around 8.5dKH. If yours was my tank, I would keep alk around 10dKH. When you have higher nutrients, it is better to raise dKH as well.

Exactly why it is like this, we dont know. But there is a well represented correlation that shows high nutrient tanks are healthy at high alk while low nutrient tanks are healthy at low alk (by healthy here I mainly mean SPS health). There was a thread that I cant find right now that listed the N, P, alk and Ca levels of tanks from a number of "successful" tanks. The coloration between nutrients and Alk/Ca was clear as day light.

I likely explanation is if you give corals lots of N and P to built soft tissue, you also better give them more carbonate and calcium to built more skeleton as well. If not, they dont have enough demand for N and P since rate at which new soft tissue is produced gets limited by how fast new skeleton can be built, this causes N and P to accumulate within the tissue and either cause the corals to brown or bleach. And in vice verse, if you dont give corals N and P to built soft tissue, dont give them excess amounts of carbonate and calcium. This causes them to waste energy trying to maintain lower internal concentration of carbonate and alk, which causes stress.

Since the problems you observe mainly center around SPS corals, an alk issue makes sense even more.

Also when your SPS die, do they bleach or necrose starting from the tips or from the base, or do regions that get more light bleach/die first?

Mind showed STN from all three. Bottom up, tip down, and the parts exposed to the light were the first to go.
 
Mind showed STN from all three. Bottom up, tip down, and the parts exposed to the light were the first to go.

What are your alk/ca and N/P numbers? Parts exposed to the light going down first makes me believe it might be an imbalance of these 4. If it was a disease based issue, they generally die from the bottom to up (aka white ring disease).
 
What are your alk/ca and N/P numbers? Parts exposed to the light going down first makes me believe it might be an imbalance of these 4. If it was a disease based issue, they generally die from the bottom to up (aka white ring disease).

Here is my thread: http://www.reefcentral.com/forums/showthread.php?t=2669333

At the time I started noticing big issues, end of January, No3 & Po4 read 1 / .02. Alk at the time was running 8.6 - 9.3dKH.

End of February:

SG: 1.026
pH: 8.1
No3: 10
Po4:.08
Cal: 422
Alk: 8.4
Mg: 1400
Temp: 80.0


Since then I've got both No3 and Phos up (10-15 & .1) which has caused some green algae to come back. Kept Alk between 7.9-8.3 over that time. Nothing is showing signs of growth at this point for several months.

* Variations in Alk range is likely the Hanna noise / margin of error.

I don't want to hijack the OP's thread, it may be more respectful to continue on mine?
 
Imo, N and P of 1 and 0.02. is too low for an alk of ~9dKH. I would have kept it around 8dHK

And Alk of ~8 dKH is too low for N and and P of 10 and 0.08. I would raise it to 9dHK, maybe 9.5 dKH.

For comparison, water around the reefs have trace amounts of N and P and dKH is around 7.

Edit, I am checking your thread now
 
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