SPS and water temperature, chiller really needed?

[Randy Holmes-Farley]

I think that's a fair and accurate statement. In a typical reef tank, how much more oxygen does a tank running at 78F compare to 88F? And how does the difference translate to an actual usage in the event of a power failure?

According to the research, the difference translates roughly to about 6 extra seconds for a single adult clownfish. In other word, you would have extra oxygen to sustain a single clownfish for 6 extra seconds at these 2 end points. Do you have data to support this claim is false?

So let's look at the claim with an eye toward actual numbers. It seems to be more hyperbole than fact.

The saturation level of O2 at 78 deg F is about 6.65 mg/L.

At 88 deg F it is about 6.1 mg/L.

I got that from this published table using 20 ppt for the chlorinty which is close to 35 ppt salinity:

http://www.ecy.wa.gov/programs/eap/models/rates_and_constants/Sect3-1.pdf

That is a difference of 9% in the total O2 available at a dead stop in flow.

So while I do not know how much O2 a clownfish uses, we can easily determine that if that 9% difference in O2 only allows it to live for an additional 6 seconds, then its total lifespan during the power failure must be assumed to be only 66 seconds. Doesn't that seem to fail simple logic in even the most inexperienced reefers idea of what happens in 66 seconds?

IMO, it seems to be ridiculous hyperbole, bringing into doubt the other statements made in support of that "opinion".

 

[dzhuo]

That is a difference of 9% in the total O2 available at a dead stop in flow.

Actually that's exactly what he claimed. The difference is roughly 6% to 9% but it's still roughly 200% above the oxygen compensation warning level at both end points (pay attention to the end remark of the quote I had above) and the percent difference disappear very quickly due to the higher metabolism rate for animals kept at lower temperature with less fluctuation. In fact, fish which had experienced greater fluctuations will use less oxygen as temperature continue to raise as oppose to those kept in a constant temperature.

In your other example where you have 2 tanks one run at 77-81F and other running at 81-85F. If both tanks were to raise to 90F (say a power failure), fish running at lower temperature would have experienced a much greater fluctuations hence higher metabolism rate which would use up this extra oxygen much faster compare to fish keep in 81-85F. The rate of acceleration will even be greater as temperature continue to raise. The 81-85F would still use up oxygen but at a slower rate compare to the 77-81F. It's not just that lower temperature holds more oxygen, it's that when the temperature raises, fish kept at lower temperature will significantly use up more oxygen due to thermal stress and higher respiration rate:

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.

I actually have asked for his data before but it's not free so I didn't follow through. It would great if you can shot him a PM to verify. I chose to believe his work because his contribution to the hobby just I trust you on everything chemistry even I will never be able to verify your work.

 

[dzhuo]

Here is the quote where the 6% to 9% he mentioned and how temperature increase correlate to oxygen consumption and metabolism in general:

Temperature? What do you use and why?

There's a lot of truth to this, but also a lot of common misconceptions and oversimplifications.

There's certainly an oxygen component to be concerned with for a few reasons. One being that warmer water holds less oxygen at saturation. However, over the range of temps we're talking about in reef tanks the difference is negligible. There's something like 6% difference going from 78-86. You have to go above 90 before the saturation point even drops below 200% of the lower safe limit.

Of course the amount of O2 the water can hold is a different story than what it actually does hold. Adey has shown that during the day the water column on the reef is often hyperoxic and then becomes hypoxic at night. The differences are even more pronounced within coral colonies and the reef structure itself. He also found that O2 in a captive reef very closely resembles that seen in nature. Eric Borneman has done some work testing more tanks with similar results. I've only taken a few readings in tanks that resemble what you see in the hobby and they were all replicate tanks, but my readings didn't suggest that oxygen was any more limited than in nature either. In some tanks very heavily stocked with fish, oxygen availability may be an issue, but in the average reef tank it doesn't seem to be.

Of course the demand for O2 does generally increase with temperature. The rule of thumb for poikilotherms is that for every 10 degree C increase, metabolism will double. Over the range of reef temps that ends up being, very roughly, 9% increase in metabolism per degree Fahrenheit increase in temp (the trend isn't actually linear, so this just gives a rough estimate). However, that rule of thumb doesn't actually represent reality. As it turns out the amount of increase actually depends on the thermal history of the animal. At a given temperature, lets say 80, an animal that normally sees an average temp of 82 actually uses less energy than an animal of the same species that normally sees a temperature of 78. As temperature continues to increase the metabolism of the individual from the colder environment increases faster than the one from the warmer.

Thermal history also sets where the stress threshold for the animals is. Lots of people keep their tanks cooler than the natural average due to the mistaken belief that the danger threshold is a set value and lowering their temp will give them more room before they reach it. That isn't the case. The stress threshold is a product of acclimation, so lowering the temperature only acts to lower the threshold as well.

Unfortunately, he hasn't been to RC since June 2011 or I would have PM him directly for the discussion.

 

[gmate]

I read this thread, got up, and turned my heater to 82 degrees. lol

 

[Randy Holmes-Farley]

OK, we are largely just arguing from different assumptions about a power failure (how long, how hot, etc) and how the data that exists impacts those scenarios. I've probably said all that needs to be said from my standpoint.

I'll continue to keep my tank cooler in summer and warmer in winter to offset the problems of a power failure.

 

[Ron Reefman]

I'll continue to keep my tank cooler in summer and warmer in winter to offset the problems of a power failure.

And I think 99.7% of us reading this thread will do the same! :beer:

 

[karsseboom]

Yes I agree with randy, what he said makes perfect sense. In the summer run the tank cooler just incase the power fails you will have time to correct it before is reaches about 85 where problems start. In the winter run the tank warmer incase power fails, you have a few hours before the tank drops below 75 to correct it.

 

[r-balljunkie]

I used to be the biggest advocate of not using a heater, another point of failure in my mind. So what if the temps fluctuated or dropped. With this logic, I never ever lost a single piece of livestock, even if my tank dropped into the 70 degree range in the winter months. I would of course run a chiller (lived in Houston TX) to keep the temps down in the summer, but did nothing to control temps in the winter. Since then, I moved to the South Pacific and spend a ton of time on the reef, literally. Whether snorkeling, diving, or reef walking, I’m knee deep into reefing. I now run a heater after realizing how warm the reef is in reality. Tide pools often get up to 90 degrees at low tide coral heads sticking out of the water for hours at a time(SPS are more resilient than we think). The open water is a constant 85 degrees, even down to 120', i never wear a wet suit diving.
With all this said, after 20 years of keeping saltwater, I now use a heater. IMO it’s not fair to the livestock to pull them out of their natural state and not provide the best environment possible. i keep my heater at 80-81 which is a compromise to what nature is, at least in my back yard.

People who run their systems down to 72-74 puzzle me….waste of BTU’s and not even close to nature.
c

 

[ivans75]

Sorry, although the discussion sounds very informative and scientific, I think this thread has gone haywire lol. This is not about "how to set temperature in winter or summer" but instead to discuss what is the actual temperature we should keep our SPS corals (not just any corals, as the title of this thread suggests).

The fact that the SPS in the nature live in the water with warm temperature. ( I didnt have my thermometer handy at that moment so I did not measure the temp of the water) But the water was warm enough for me, infact it was great to swim and snorkle around. I know how cold is 26 degree celcius is, it is not certainly 26 not even 27, I believe the water was around 28 or even 29 degree celcius. It was on low tide at Sarangan, Bali.

Remember your SPS comes from this country, where I live, theres no winter here. Constant 31-33 on the outside on day time and 27-29 on night time. 27 is the minimum even on rainy season.

 

[ivans75]

I used to be the biggest advocate of not using a heater, another point of failure in my mind. So what if the temps fluctuated or dropped. With this logic, I never ever lost a single piece of livestock, even if my tank dropped into the 70 degree range in the winter months. I would of course run a chiller (lived in Houston TX) to keep the temps down in the summer, but did nothing to control temps in the winter. Since then, I moved to the South Pacific and spend a ton of time on the reef, literally. Whether snorkeling, diving, or reef walking, I'm knee deep into reefing. I now run a heater after realizing how warm the reef is in reality. Tide pools often get up to 90 degrees at low tide coral heads sticking out of the water for hours at a time(SPS are more resilient than we think). The open water is a constant 85 degrees, even down to 120', i never wear a wet suit diving.
With all this said, after 20 years of keeping saltwater, I now use a heater. IMO it's not fair to the livestock to pull them out of their natural state and not provide the best environment possible. i keep my heater at 80-81 which is a compromise to what nature is, at least in my back yard.

People who run their systems down to 72-74 puzzle me"¦.waste of BTU's and not even close to nature.
c

This is true, in tide pool where SPS are there and thriving, the water is amazingly warm, very warm. I went to a place in west java coastal area and found so many carpet anemones in low tide where water was only like 60 cm deep and it was warm. Gonioporas were everywhere, favias and the like too. We should stick to what nature has for our corals.

 

[1stMars]

hey ivan i know this pst is 2 years back. So what tank temp are u keeping at ur current tank?