keeping water at 72-75 vs 80 degrees?

[geaux xman]

what else changes besides the temp?

such as oxygen content, fish less active? bacteria growth less likely? fish appetite?

 

[Dr Colliebreath]

More dissolved oxygen at lower temps. I would thing their metabolism would increase, requiring more food. The big question is whether that affects biological processes negatively, such as is a particular chemical process impaired to the point it causes a problem. People seem to think cooler water fish don't do well at higher temps for extended period. This would seem to be the flip side of that problem. We need a fish biologists to explain.

 

[D5HP]

I have heard of accelerated growth rates at higher temperatures but that could be just sharks. Not certain!

 

[Allmost]

More dissolved oxygen at lower temps. I would thing their metabolism would increase, requiring more food. The big question is whether that affects biological processes negatively, such as is a particular chemical process impaired to the point it causes a problem. People seem to think cooler water fish don't do well at higher temps for extended period. This would seem to be the flip side of that problem. We need a fish biologists to explain.

at lower temp, fish eats LESS, as it burns LESS.

higher temp, higher bacteria methabolism [that is why we keep bacteria cultures in fridge, also Phyto .. to slow down their process] fish would eat more.

 

[Recty]

From what I recall...

Lower temperature water holds more oxygen.
Lower temperature water slows metabolism. Something like every 10 degrees Fahrenheit decreases metabolism by half in water. The inverse is true with increasing temperature, which is why people recommend raising the temp when you have ich and are treating it, because the life cycle will be shortened.

Fish appetite would, I believe, be lessened, with a drop in temperature. Food would digest slower also.

Bacterial growth would be less.

In the end, I'd rather run my tank a couple degrees cooler than a couple degrees warmer. However, I have fish only, not corals... if I kept corals I dont believe I'd drop much below 78-80.

 

[C0rp]

The amount of dissolved oxygen between tanks at 80 or 76 is so minimal that it really makes no difference...or so I have read at least. I don't even think its a single % difference IIRC.

 

[Federer]

I have observed that my corals/clams are more vibrant at 80 vs 75 degrees and fish are less skittish. Just my observations.

 

[namxas]

The biggest reason folks keep SH at <75*F is because at that temp, bacterial growth begins to really take off, and SH are very prone to getting bacterial infections in closed systems.

We keep all of our setups at <76*F, except the SH (74*F max) and the bluefin lionfish (63*F max). IME, most everything benefits from this as well as the higher O2 content. In fact, when I kept my softy/clam reef, it would "tell" me when the water hit 80*F back in the old days because they wouldn't do as well, and at about 82*F the clams and some of the corals definitely weren't happy campers.

 

[clayspst]

i run my reef tank at 76 all the time with no problems

 

[snorvich]

i run my reef tank at 76 all the time with no problems

All my tanks are at 76F (reef)

 

[Dr Colliebreath]

I was thinking that, as in the case of other animals such as mammals, the fish would expend more energy to maintain body temperature. However, it appears that fish don't do that, but instead let their body temperature adjust to surroundings. I found this on a quick search: http://www.fao.org/docrep/X5738E/x5738e03.htm. It references freshwater fish, but I imagine saltwater fish are pretty much the same.

As the fish isn't maintaining its temperature internally, the biological processes will be operating at the lower temperature of the aquarium. Are they affected by somewhat lower (say 5 degrees) temperatures?

 

[geaux xman]

Well my fish only is at 80degrees not by choice, and thats with just the room fluorescent lights on. That particular room doesnt get good A/C. My small 17g in the bedroom stays around 74-75degrees. Also the return pump and skimmer pump might be responsible for a couple degrees there.

I'm considering getting a 1/3HP chiller to run my FO at 73-74degrees.

 

[dzhuo]

However, it appears that fish don't do that, but instead let their body temperature adjust to surroundings.

Yup. Most tropical reef animals have no problem handling temperature swings and there is absolutely no evidence that higher temp (such as those commonly seen in reef tank between 78F to 85F) are stressful to fish or corals. There is evidence, however, suggesting that temperature swings are important for thermal stress regulations. Here is a quote from researcher who specialize in thermal stress in anemone and clown 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.

 

[dzhuo]

The amount of dissolved oxygen between tanks at 80 or 76 is so minimal that it really makes no difference...or so I have read at least. I don't even think its a single % difference IIRC.

Dissolved oxygen at 78F and 90F is less than 6%. Both end points still holds more than 200% of oxygen above the depletion warning zone. In other word, if you have 2 tanks which are identical and one runs at 78F and another run at 90F. The 78F tank would hold roughly more oxygen for a typical clown fish to breath for ~6 seconds. The difference is so small, it's not even worth mentioning.

 

[Biggar]

I keep my reef tank at 80-82. Everything is fine. No worries man

 

[curlykid]

81 during the day. 79 at night.

 

[Recty]

Well my fish only is at 80degrees not by choice, and thats with just the room fluorescent lights on. That particular room doesnt get good A/C. My small 17g in the bedroom stays around 74-75degrees. Also the return pump and skimmer pump might be responsible for a couple degrees there.

I'm considering getting a 1/3HP chiller to run my FO at 73-74degrees.

Have you tried the evaporative cooling I mentioned in your other thread about it? I bet you could drop 2 degrees, maybe even three, just by using that method.

 

[dlterry85]

keep mine at 78-82 with no chiller and everything thrives.

 

[Amoore311]

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.

Would this suggest that animals commonly known to need lower temps due to collectiong depth do not actually need those cooler temperatures? I'm thinking along the lines of Bandit Angels, Interuptus Angels, etc.

 

[Korrine]

dzhuo,

who is the researcher?