Temperature question

[Cantgrowdidly]

If the tank is running 78-83 should I raise the heater to reduce the swing or let it be?

 

[phishsauce]

Yes, if you want to save electricity.
Do you have it on a controller? Mine is connected to an apex which turns on the heaters if it's below 70 degrees. And it doesn't always hit that number here, it's usually over.
But it saves me a lot of electricity.

78-80 degrees is ok, as far as temps, but over 82, you may need to becareful about the corals stressing out, not to mention fish if you have any.

 

[dzhuo]

If the tank is running 78-83 should I raise the heater to reduce the swing or let it be?

Totally fine. Absolutely nothing to worry about.

 

[sjfishguy]

Totally fine. Absolutely nothing to worry about.

Really? I think a steady number is much more important than actual temp. So either make it 78-79 and hold it there, or 81-82 and hold it there. The swings of anything is what stresses corals.

 

[dzhuo]

I think a steady number is much more important than actual temp.

That's what we used to believe which is incorrect.

So either make it 78-79 and hold it there, or 81-82 and hold it there. The swings of anything is what stresses corals.

Temperature is an exception. There is no evidence that normal swings inducts stress response in corals or fish. In the wild, it's not unheard of to record up to 6 degrees of swings within a couple of hours. Temperature fluctuations covers a large range from the low end of 76F (winter average about 78F) to low 90F (summer time average about 82F) so corals have adopted to these types of fluctuations their entire evolution history. Normal temperature fluctuations are important for corals to build thermal resistance and is a natural process for them; not stress. Most people who keep a constant temp really does nothing but to "hurt" the corals in the event of equipement failures. The biggest argument of keeping reef tank at lower temperature is oxygen threshold. It's true that at lower temp, water holds more oxygen but the difference is extremely small. For example, at even 90F, any typical reef tank still holds more than 200% of oxygen above the warning level. From 78F to 90F, the difference is roughly 6%. In other word, your tank (which runs at 78F) would have more oxygen for a single adult crown fish to breath for an extra of 6 seconds (compare to a tank running at 90F). It's really nothing. Other than that, I have seen a few research papers suggest that spawning events are tied to temperature (along other variables) but the conclusion isn't definite.

Here is a quote from a researcher specialize in thermal stress (his work is focused in anemone and fish):

I work on thermal stress in reef animals, no naturally threads on this subject aggravate me because there's so much misinformation in the hobby regarding temperature and it's constantly being repeated as if it were fact.

To answer the original question, I let my tank get up to 86 regularly. On rare occasions it might climb to 88. Last year during a power outage it went to 92 for a few hours without issue.

Now to address the misinformation about what is harmful and what isn't when it comes to temps-

What kinds of temps are reefs seeing in the wild? The worldwide, yearly average is about 82. The average wintertime low is 77 and the average summertime high is 86. The often repeated "ideal" temperature of 78 replicates the low end of wintertime temperatures. Also, it has been documented that the minute-to-minute fluctuations in temperature are regularly as much as half of the yearly range with the magnitude of fluctuation increasing with depth down to 90-120 ft. There is absolutely no evidence that these fluctuations are stressful to reef animals, nor would you expect them to be since they have experienced these fluctuations for their entire evolutionary histories. In fact, there's limited evidence suggesting that these types of fluctuations may be important for modulating the stress threshold.

So if 78 isn't ideal then what is? For the hard corals we have optima for, it's about 82-84. That's also roughly the average for the area of the Indo-Pacific that represents the center of coral reef biodiversity. That's probably pretty close to the ideal average temperature.

How high is it safe to go? It depends. The answer varies from tank to tank. The stress threshold is not set genetically. It changes depending on the ambient temperature regime. The simple answer is that you're safe to go 2 degrees above the normal maximum temp. That's why it really bugs me to see statements like "above X degrees is just asking for trouble." It all depends on what the temperature normally is.

Another statement that bugs me is "a colder temp offers a wider margin of error in case of an emergency." This assumes that 1) the stress threshold is a set number, which as I already pointed out isn't true, and 2) that the animals in a cooler tank will respire less if there's an emergency. There's not much data on the second assumption, but from the little we have that assumption doesn't seem to be true. At rest, under normal conditions, if you have one specimen (A) at 78 deg F and another (B) of the same species and the same size at 80 deg F, then B will have a higher respiration rate than A. However, as the temperature increases, the respiration rate of A quickly out-paces that of B and for any further non-lethal temperature, B will always be consuming less oxygen than A. In other words, at 80 degrees, A will use more O2 than B does at the same temp. The same is true for 82, 84, etc.

The difference in O2 saturation over the range of temps we keep in reefs is so small that it's essentially negligible. Even at 90, the saturation point is still double the safe lower limit.

This topic has come up over and over.

 

[tebstan]

Interesting stuff! Do you have any links to more of his research?

 

[dzhuo]

His work is not free but he's a RC member and have contributed to this topic significantly. I PM you his info.

 

[RynosReef]

Interesting... I've never heard that before but it does make sense. Thanks for the info. So basically an acceptable temp swing can help toughen up the corals. I wonder though with sps demanding so much stability, would a large daily swing slow down growth? I realize in the wild they go through large temp swings and are even exposed to air. But after all, the tanks we keep corals in are vastly smaller than the ocean. They are comparable in some aspects but not all. For example I wouldn't purposely expose my corals to air. Or stop managing nutrients and ca and Alk because the ocean takes care of that in the wild. Please don't misunderstand and think im disagreeing. It's just a new thought for me so I have to question it a little. Maybe there should be a balance. Allowing a larger swing say 5 degrees from the normal temp would be ok. But allowing swings up to 90 from 80 might be a bad idea?

 

[rmalone]

I really don't see how you would save electricity by raising the heating set point. If anything it would cost more electricity. If you raise your heat set point your going to raise your average daily temperature and your going to do that via electricity. Your 83deg high is coming via ambient temp which is free. Electricity is not, and electricity is how your going to raise the low temp point.

If your only hitting 83deg then I wouldn't worry about it at all, much above 83deg and I would get nervous. I am guessing that your seeing 78deg at night and peaking at 83deg in the afternoon? I wouldn't worry about it. If you were doing that hourly it might be a problem.

 

[dzhuo]

I wonder though with sps demanding so much stability, would a large daily swing slow down growth?

I have not seen any research paper on this so I can't say conclusively yes or no. My guess would be no and it shouldn't matter much. However, it seems to me calcification happens fastest around 82F but I can't find the research paper anymore.

I realize in the wild they go through large temp swings and are even exposed to air. But after all, the tanks we keep corals in are vastly smaller than the ocean. They are comparable in some aspects but not all. For example I wouldn't purposely expose my corals to air. Or stop managing nutrients and ca and Alk because the ocean takes care of that in the wild. Please don't misunderstand and think im disagreeing. It's just a new thought for me so I have to question it a little.

Yes I totally agree. Comparing an open and close system is not always apple to apple but I don't think this plays a huge role when it comes to temperature. Interestingly, our tank is considered to be an open system while the ocean is considered close contrast to what we generally believe.

Maybe there should be a balance. Allowing a larger swing say 5 degrees from the normal temp would be ok. But allowing swings up to 90 from 80 might be a bad idea?

Yes I wouldn't purposely let it swing up to the 90s. I think despite everything said, I would be comfortable with anything between 77F and 86F. My tank swings between 79F and 83F daily in the summer.

 

[sjfishguy]

I have personally had corals appear stessed with swings as wide as you claim are acceptable. I would like to see some hard evidence of this research, not just a post. It is good information and I like old myths going by the wayside, but I will stick with my constant temp for now.

It makes sense though, as I know currents, wind, sunshine, etc. can all make temps swing quite wildly. I won't be the guinea pig to try this out in my reef though

 

[dzhuo]

I have personally had corals appear stessed with swings as wide as you claim are acceptable.

Well, that's what happen when you keep the temp constant. That's precisely why I said people who keep constant temp is "hurting" the corals. The question really is why a minute temperature fluctuation stress the corals when they have experience much larger swing for millions of years.

It makes sense though, as I know currents, wind, sunshine, etc. can all make temps swing quite wildly. I won't be the guinea pig to try this out in my reef though

You don't have to because lots of people have tried it. A quick Google search would yield lots of research papers why temperature fluctuation has never shown to induct coral or fish stress. I am happy to PM you the info but here is another one from Chris (PhD who has done a lot of research - yes including published data publicly - on calcification):

The rate of calcification for most corals peaks at or 1-2 deg. C below the normal summer maximum temp and then quickly drops off above that temp. due to physiological stress/bleaching. The normal summer time high on most reefs is 84-86 F. Thus, most corals will reach a maximum rate of calcification between 80 deg. F on the low end and 84-86 F on the high end. If one is trying to maximize growth it makes no sense in the world to keep an aquarium below 80 deg F. Averge reef temperatures are higher than that anyway. Temps. lower than 80 F and especially lower than 78 F are essentially winter temps and corals tend to grow substantially slower in winter. I also wouldn't go over 84 F in an aquarium intentionally though. Above the normal summer max. the rate of calcification drops like a rock and one tempts all kinds of other problems with elevated temps. too.

See:

Coles, S. L., and P. L. Jokiel (1978), Synergistic effects of temperature, salinity and light on the hermatypic coral Montipora verrucosa, Mar. Biol., 49, 187– 195.

Houck, J. E., R. W. Buddemeier, S. V. Smith, and P. L. Jokiel (1977), The response of coral growth and skeletal strontium content to light intensity and water temperature, Proc. 3rd Int. Symp. Coral Reefs, 2, 424– 431.

Marshall, A. T., and P. Clode (2004), Calcification rate and the effect of temperature in a zooxanthellate and an azooxanthellate scleractinian reef coral, Coral Reefs, 23, 218– 224.

If that's not enough, feel free to PM me and I will direct you to even more research papers. As I mention earlier, there is absolutely no evidence that this sort of fluctuations are stressful to corals. The best you will find is a research paper done in the 80s on fresh water which does not apply to salt water.

 

[cnote2991]

This is interesting and a new concept to me also. I have always been trying to keep temp within 1.5 degrees. This does make sense though. Where i live i am always fighting heat. I have my chiller set to come on at 80 and turn off at 79.

I'm thinking about setting it to turn on at 82 and turn off at 79. if this cycle happens several times a day could it be bad? instead of 1 big swing having several throughout the day?

 

[dzhuo]

I'm thinking about setting it to turn on at 82 and turn off at 79. if this cycle happens several times a day could it be bad? instead of 1 big swing having several throughout the day?

That's totally fine. Even if you try very hard, you won't be able to replicate the kind of fluctuations seen in their natural habitats (not that I would suggest you do). However, if your corals are already accustom to constant temp, you will need to introduce the change slowly.

 

[sjfishguy]

So you are saying 80% of people on RC keep their tanks at too low a temp?

http://reefcentral.com/forums/showthread.php?s=&threadid=725213

 

[dzhuo]

So you are saying 80% of people on RC keep their tanks at too low a temp?

If we assume the poll is correct and have enough data points then yes that's what I am saying. I am not surprise most people run their tank much lower than what it should be given how wide spread this myth has been. Most books you pick today still insist that temperature fluctuations (within reason) are stressful for corals. I personally know at least 2 researchers contacting a few well respected authors asking them to stop the false information but nothing is stopping the publishers continue to publish their books. It's just unfortunate.

The other story, obviously, is that running your tank at 78F (or a degree lower) is fine as well. That's nothing wrong; it's just that you subject the corals to their winter time temperature 100% of time which isn't what they used to. Generally, there is no right or wrong answer when it comes to temperature. There is not a genetically set point. Corals are very adoptive to temperature swings.

 

[sjfishguy]

Its a very interesting topic. You are just the first and only person I have ever heard say this. Not saying you are wrong, but kinda like you telling everyone the earth is round when we all think its flat, its gonna take a lot of convincing. I would like to hear some other points of view, I hope we can keep this topic going

 

[dzhuo]

No offense Rich but I am not the only one telling people that temperature fluctuations aren't stressful to corals and fish. There are a lot of research papers done in this area. There are a handful of researchers in RC alone and has been advocating people over the years what we used to believe stability in temperature is simply incorrect. Here is another research paper done in 2008:

Results of the study indicated that the symbionts of the corals that were exposed to the 48-hour pre-bleaching thermal stress "were found to have more effective photoprotective mechanisms," including "changes in non-photochemical quenching and xanthophyll cycling," and they further determined that "these differences in photoprotection were correlated with decreased loss of symbionts, with those corals that were not pre-stressed performing significantly worse, losing over 40% of their symbionts and having a greater reduction in photosynthetic efficiency," whereas "pre-stressed coral symbiont densities were unchanged at the end of the bleaching." In light of these findings, Middlebrook et al. (2008) say their study "conclusively demonstrates that thermal stress events two weeks and one week prior to a bleaching event provide significantly increased thermal tolerance to the coral holobiont, suggesting that short time-scale thermal adaptation can have profound effects on coral bleaching."

This study also looked at various coral reef sites (as oppose to corals kept in tanks) and the conclusion is the same.

In addition, they found that the "coral genera most susceptible to thermal stress (Pocillopora and Acropora) showed the greatest increase in tolerance."

As for the significance of these and other observations, the Australian scientists say that "the range in bleaching tolerances among corals inhabiting different thermal realms suggests that at least some coral symbioses have the ability to adapt to much higher temperatures than they currently experience in the central Great Barrier Reef," citing the work of Coles and Brown (2003) and Riegl (1999, 2002). In addition, they note that "even within reefs there is a significant variability in bleaching susceptibility for many species (Edmunds, 1994; Marshall and Baird, 2000), suggesting some potential for a shift in thermal tolerance based on selective mortality (Glynn et al., 2001; Jimenez et al., 2001) and local population growth alone." Above and beyond that, however, they say their results additionally suggest "a capacity for acclimatization or adaptation."

Almost all research papers point out the obvious: Letting temperature swings only helps the corals to build better thermal stress tolerance and is not stress to them at all. This is something corals are very capable of adapting to.

Here is link to the summary and lots of references:

Coral Reefs (Responses to Temperature Stress) -- Summary

 

[doctorgori]

From 78F to 90F, the difference is roughly 6%.

"just 6%" in O2 could be actually be a meaningful difference)

heck, just the difference between 65F-70 is enough to stop many salmonoids from inhabiting a river, lake, stream...

...anyway I get it if your point is that corals might not be all that sensitive to temp variations as we suspect

 

[ksc]

The temperature myth is based on those cheap thermometers that have a shaded section between 70-80. My tanks rarely get below 80, and have thrived for years.