Temperature stability

[BeanAnimal]

I keep hearing time and time again about temperature stability and the best operating temperatures for a reef tank.

I have read a dozen or so websites, some hobby related (OZ REEF, and Shimek) and others natural reef related. I also understand that our systems are not natural reefs and what works in nature may not work in our systems for a myriad of reasons, including but not limited to, oxygen, nutrient levels, lighting and other differences between NSW and SSW and our systems.

It appears to me that most of the worlds reefs have a daily temperature swing of 2-5 degrees F over the 24 hour day cycle. In addition the average temperature swings anywhere from 8-15 degrees F per season.

I am not convinced that "random" temp swings due to lights and heaters or other artificial environmental stimuli is healty, but it would sure appear that a program to simulate daily and seasonal temp changes would surely benefit out corals. (I feel the same about daily and seasonal lighting cycle lengths as well).

I also feel that most folks run their tanks at a somewhat low temperature average. I do understand that oxygen levels arehard to maintain in an 82-84 degree tank, but with proper water agitiation and turnover (ex. a skimmer) this should not be a problem.

Thoughts?

 

[Weatherman]

There are a couple of ways to think about thisââ"šÂ¬Ã‚¦

Firstââ"šÂ¬Ã‚¦ although daily and seasonal swings in temperature are common in the natural environment (with variability being more extreme in tide pool and reef flat areas), any kind of temperature swing is stressful. Animals may have adapted to those conditions, but that doesnââ"šÂ¬Ã¢"žÂ¢t mean that the temperature swings donââ"šÂ¬Ã¢"žÂ¢t take their toll. Itââ"šÂ¬Ã¢"žÂ¢s much easier to live in a location where the temperature is constant, or changes slowly, than one where the temperature is extremely variable and changes rapidly. Thatââ"šÂ¬Ã¢"žÂ¢s one of the reasons why we highly adaptive humans like to live in homes and offices where the temperature is a constant 72F and relative humidity is a constant 40% (or, whatever your temperature and humidity preference may be), even though we can do ok in extremely cold or extremely hot conditions.

On the other handââ"šÂ¬Ã‚¦ animals use changes in temperature, length of day (or length of night), and salinity, as signals for certain life events, like spawning. Environments, where the temperature, salinity and length of night are constant, provide none of those signals. Is this a stress? I donââ"šÂ¬Ã¢"žÂ¢t know. I guess it depends on how much a sense of seasons effects an animalââ"šÂ¬Ã¢"žÂ¢s well being.


As far as specific temperatures are concerned, recent bleaching events suggest many coral live at the upper end of their temperature tolerance range (especially during the summer months). If you wish to take the approach that your animals appreciate knowing what season it is, you could slowly adjust your tank water temperatures from the upper 70s during the winter to the mid 80s during the summer, as long as you were careful not to let things get too warm. You should, also, adjust your photoperiod at the same time, with a shorter photoperiod in winter and a longer photoperiod in summer. The period of maximum photoperiod length should precede the period of maximum temperature by about two or three months (same for the minimum).

If your philosophy is that your animals should live in a low-stress environment of, essentially, constant spring, then you should keep your temp around 80F and your photoperiod constant year round.

 

[BeanAnimal]

In designing my software for my controller, these are the exact conclusions and "options" I have come up with. I also read several of the "bleaching" studies and it does seem that there is an upper limit that the corals can withstand. This limit is of course different for different corals and different habitats.

My tank runs between 80-84 as. I could keep it cooler in the winter, but the summer dictates that my temp rises to about 84 in the day. I may look into a small chiller to drop this a degree or two.

My question is also one of "stress". Is the stress due to the temp swings really stress, or is it a built in expectation that if not met causes stress? I know these animals don't have brains, but the do have nerver networks that obviously do pick up environmental signals and act upon them (spawning is of course an example).

Thanks for the reply

Bean

 

[Weatherman]

<a href=showthread.php?s=&postid=6936689#post6936689 target=_blank>Originally posted</a> by BeanAnimal
My question is also one of "stress". Is the stress due to the temp swings really stress, or is it a built in expectation that if not met causes stress? I know these animals don't have brains, but the do have nerver networks that obviously do pick up environmental signals and act upon them (spawning is of course an example).

Thanks for the reply

Bean

I donââ"šÂ¬Ã¢"žÂ¢t know if many marine fish, or mobile marine invertebrates, actively change location in response to change in temperature, but I think weââ"šÂ¬Ã¢"žÂ¢re all familiar with reptiles moving into the sun to warm up in the morning and moving into the shade to cool off during the afternoon.

Thereââ"šÂ¬Ã¢"žÂ¢s clearly an advantage to an animal to maintain constant internal temperature within some optimal range, and, at least with reptiles, they will respond to the stress of external temperature change outside of their optimum range by moving from one location to another. If they canââ"šÂ¬Ã¢"žÂ¢t move, hopefully they have adapted to live in temperatures outside their optimum, but it doesnââ"šÂ¬Ã¢"žÂ¢t mean their bodies will work most efficiently at those temperatures.

 

[BeanAnimal]

I understand the analogy, but do not see where a fish could "go" in response to a temperature swing, other then deeper into cold water. I am not aware of an studies (but they may exist) that show the movement patterns of reef fished in response to daily or season temperature changes... May be something interesting to look into.

Bean

 

[Weatherman]

<a href=showthread.php?s=&postid=6937958#post6937958 target=_blank>Originally posted</a> by BeanAnimal
I understand the analogy, but do not see where a fish could "go" in response to a temperature swing, other then deeper into cold water.

That would be my thought.

There are, probably, some fish that go out on the reef flat late at night and during the morning, when it's cool, to feed, and then move out into deeper water during the afternoon and evening. There may be nothing to eat out there in the deeper water, but at least they won't have to put up with the stress of the water temperature going up by several degrees.