It happens on the Reef: so it must be so!

[doctorgori]

I was just reading another topic about what are acceptable temperature fluctuations
http://www.reefcentral.com/forums/showthread.php?t=2108616
.... and a well articulated post about corals tolerances in a natural environment to temp fluctuations....
http://www.reefcentral.com/forums/showthread.php?t=1977164
my take away was since that is the natural state of things, perhaps the same tolerances should apply to captive specimens....

Now I'm not endorsing or debunking that assumption, but it got me to thinking and reconsidering if our quest towards wholesale duplication of natural variables (towards a xerox copied reef "nirvana") is the right one...

Take temp fluctuations and coral hardiness: does exposing a coral to temp fluctuations in of itself make them hardier? or does that in concert with nutrition or some hidden variable contribute to a corals resistance to external environmental stresses?

...in short, can we actually provide our captive specimens with all the "tools" & resources it takes to make them hardier? or should we "coddle" them a lil because of the shortcomings of captivity?

...and in a broader scope, what natural variables should we even bother to duplicate?

 

[Amoore311]

I'm a firm believer in the fact that corals which are exposed to temperature swings, will become accustomed to those swings and deal with it just fine. Whereas corals that in a tank that is 77.5 24/7 will most certainly be shocked with temperature swings as small as 2-3 degrees.

I've seen this my self when I had 2 tanks ups w/ very similar water parameters.

My 29 Gallon tank would never fluctuate temperature at all since I ran a chiller on there. I had it set at 77, and at most the temperature would move .5 degree. My 180 Gallon reef typically saw temperature swings of 2-3 degrees daily during the summer months, and around 2 degrees max in the fall and winter.

My chiller took a crap on my one summer, and the best I could do with fans and floating ice bottles in the tank was keep the temp swing to around 3 degrees. During that fluctuation I ended up bleach out a couple LPS, and some SPS frags. No corals in the 180 ever bleached at all. The LPS were different corals between the 2 tanks, but I did have the same exact sps frags in the 180.

The lighting and source water were exactly the same, both tanks carbon dosed (Vinegar), and the maintenance schedule was exactly the same.

Yes it could have been other variables since they weren't on the same system. In my opinion, being VERY involved with both tanks, it had to be the temperature.

 

[KafudaFish]

^ this is why I don't worry about temperature.

Natural systems have fluctuations and these changes can trigger certain behaviors like spawning etc.

 

[jdhuyvetter]

I set my chiller kind of high (80). This allows daily swings of 2-3 degrees in the summer and 4-5 degrees in the winter (based on room temperature). No problems here. My low never drops below 75 and it never gets above 80.

 

[atreis]

Take temp fluctuations and coral hardiness: does exposing a coral to temp fluctuations in of itself make them hardier? or does that in concert with nutrition or some hidden variable contribute to a corals resistance to external environmental stresses?

Temp fluctuations stress the corals. It can be convenient for us to allow them though because of mechanical limitations in our systems. It's not so much people wanting to have temp fluctuations in order to recreate a natural reef (more on that in a minute), as wanting to be able to allow them in order to save energy, have a higher hysteresis on the chiller, and other convenience things like that.

Some of the temp fluctuations as they occur in a natural reef would be very difficult to reproduce in our systems, especially as they occur on the reef face (deep water facing side). Why? Water wells up from the deep that is cool, washes over the coral, and dissipates - it's a momentary event that only lasts for a few seconds. Reproducing that in our systems would be extraordinarily difficult. In addition there are the longer term trends (some warming during the day/cooling at night in calmer parts of the reef, as well as seasonal variation). These are the ones that we want to allow for convenience.

Harmful? Beneficial? Possibly... It'll cause stress. In a healthy animal, the results of small amounts of stress can be beneficial - prompting reproduction, new growth, and the like. In an only marginally healthy or unhealthy animal, those same stresses can cause it to bleach or worse. Given the closed nature of our systems, we generally work to reduce as many stresses as we can, knowing that there are still quite a few that we can't adequately control. By controlling the ones we can we hope to make an environment that is "good enough" that our animals will be healthy enough to not be hurt by the stressors that we can't control.


Me? I run my tank cooler in the winter than in the summer, and allow larger temp swings (hysteresis) in the summer in order to keep the chiller from cycling on/off too often.

 

[doctorgori]

yeah that one thread was pretty good...but my only pause would be thinking that "Captive" corals can't be nearly as hardy as wild corals given the incompleteness of whatever variables contribute to their overall health (of course thats speculative also)

...but then again one could argue that the fact they even grow/thrive when living in ASW, under T5 lighting and fed commercial foods is a testament to their adaptability...

...to rephrase: just wondering what parameters are actually critical anymore and which ones should we try to mimic as close as possible (from a environmental standpoint)?

 

[doctorgori]

In a healthy animal, the results of small amounts of stress can be beneficial - prompting reproduction, new growth, and the like. In an only marginally healthy or unhealthy animal, those same stresses can cause it to bleach or worse. Given the closed nature of our systems, we generally work to reduce as many stresses as we can, knowing that there are still quite a few that we can't adequately control. By controlling the ones we can we hope to make an environment that is "good enough" that our animals will be healthy enough to not be hurt by the stresses that we can't control

^^^ that is very well articulated, but to expound on that; my question then is:
"environmental stress" as a contributory factor towards resistance is one thing
...but certainly it must be used in conjunction to some other (perhaps dietary) variable which then contributes to longer term health/resistances

...my analogy would be vitamin C (allegedly) as being contributory to disease resistance in humans...its not like we can simply expose ourselves to cold temps and voilà', we are resistant to colds

So I said all that to say, given the restrictive and limited resources of a captive environment, is it safe to just assume we duplicate natural stresses and voilà': hardy corals?

 

[billsreef]

I set my chiller kind of high (80). This allows daily swings of 2-3 degrees in the summer and 4-5 degrees in the winter (based on room temperature). No problems here. My low never drops below 75 and it never gets above 80.

Same here.

Some of the temp fluctuations as they occur in a natural reef would be very difficult to reproduce in our systems, especially as they occur on the reef face (deep water facing side). Why? Water wells up from the deep that is cool, washes over the coral, and dissipates - it's a momentary event that only lasts for a few seconds.

Actually such upwelling can last for hours or days when influenced by winds and storms. I've dove on reefs one day with water temp around 86, returned the next day after a storm blew through to find wind induced upwelling had dropped the water temps on the same reef down to 75. Pretty good temp swing that occurred in short order, and lasted for nearly 24 hours before the upwelling ceased and allowed the water temp to come back up to the mid 80's. Sort of thing happens all the time on reefs that boarder deep water.

So I said all that to say, given the restrictive and limited resources of a captive environment, is it safe to just assume we duplicate natural stresses and voilà': hardy corals?

While I think some temp swings can help corals be acclimated to them, I also think they need to be healthy in order to handle it as well So that brings up other needs, not just temp.