Is a 2.5 degree swing in temp ok?

[mos90]

On my 125g with mh's I'm getting a 2.5 deg temp swing daily from 77.5 to 80. Is this too much for sps's to handle?

 

[ryanrid]

fine

 

[flamron]

Yep - I was swinging from 81-84 on my 75 before I put a fan on it.

Then I started swinging 80-82.

 

[rivahodges]

You should be fine.

 

[joker295]

its fine... i swing from 77 to 81 with no issues on my 250 system

 

[mos90]

Ok great. I might still get a few fans to minimize the swings. I really didn't want to buy a chiller.

 

[dzhuo]

2.5 degree is absolutely nothing to worry about. In fact, corals can handle a much larger swing (several degree hourly). Here is a quote from a researcher who specialize in thermal stress 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.

My tank swings from 79F to 84F daily during the summer (right now). In the winter time, it goes from 77F to 81F. Thermal fluctuations is important for almost all reef animals and minimize temperature swing only makes them more susceptible to smaller range of stress threshold and is not natural to the corals.

 

[xcorallusx]

Ive noticed that if you let a swing from 75-82, thats safe, if they are used to it... If you get corals from someone who keeps their tank at a constant 80, and you let them swing, chances are they are going to be ****ed or RTN. I have also noticed that corals exposed to a gradual night and day temperature fluctuation, are hardier and wont get stressed and die if a problem does occur randomly. SPS wont necessarily die the first day if you let the tank get over 84, it will be a week later or so. I have my apex cut the lights off when the tank gets over 82.5, which is rare. I think the temperature fluctuation is natural and keeps the corals healthy/hardy and helps save electricity. If you are going to expose them to fluctuation, try and keep the corals in a similar range, and adjust them to the new temperatures gradually.

 

[mos90]

most of the time the temp never gets above 79.5. i keep the room temp at 70deg in the summer with my central air. but when it get very hot outside thats when i notice the tank temp getting closer to 80deg. in the winter the room temp is at 66, the tank temp should stay much cooler.

 

[sullyfish]

Ive noticed that if you let a swing from 75-82, thats safe, if they are used to it... If you get corals from someone who keeps their tank at a constant 80, and you let them swing, chances are they are going to be ****ed or RTN. .

+1 as long as your corals are used to it it will be fine. My tank temp in summer will go between 78-81 no problems.

 

[Dog boy Dave]

Mine goes from 77.6 in the morning to 83 after the lights run a few hours every day. I start tuning out lights if it gets past 83.5 just because. Had a spike to 90 or maybe a lil more about 60 days ago. Lost one smooth skined coral that might have been a true deep water and had some base erosion on my nanas and validas imediately My hawkins also browned imediately. The Hawkins lost some tissue about 30 days after the event. Other than the smooth skined colony, all of the other corals recovered. I think the daily temp swing helped the corals when they were subject to the 90 degree event.

 

[njreefermadness]

I had a spike to 90 degrees last summer (chiller plug worked loose). Only lost 2 colonies, purple plasma and a A. Turaki. Small swings are not a problem, and an occasional trip to the mid to upper 80's is not a death sentence either, but that is not where you want to be. Lower 80s, I see no problem in my experience.

Herb

 

[REEF SMAC]

Not a problem.