Maximum Sustainable Coral Temperature

[Eric45]

Science really is accidental as I learned recently when I discovered I'd been keeping the tank temperature at 84 degrees for a sustained period of time -- at least 3 or 4 months. At that point I began to notice, my lps corals were not doing well, nor were my softies. The SPS weren't growing fast, but seemed ok. Over the next few weeks, I lost an anemone, several acans, a scolemia, a brain coral and a few others.

Once I dropped the temp. things continued to deteriorate for some time, perhaps a month and only now am I seeing some recovery. I also noticed the sps growth on the rocks had retreated quite a bit.

I say all this because I believe my mistake has provided some solid empirical evidence of the actual temperature that will limit coral survival over time. As a diver I know that the Keys water is about 80 or 81. The Bahamas and Virgin Islands can warm to 83. So my guess is we are pretty close to seeing much bigger problems then we've witness so far in terms of coral bleaching.

My experience clearly showed that in my tank, 84 degrees is unsustainable over time for virtually all of my corals, although the sps did fare better than the others. While I'd really like to see this experiment repeated, I wouldn't recommend it to hobbyists. One more thing, over the time period, there were no other variables I can think of to account for the coral decay - lighting, filtration, salt, food, parameters all the same. But there's a lots of variables in the wild that might change the dynamic as far as actual temp. is concerned.

 

[outy]

My tank has swung between 72 and 82 for some 25 years.

Coral does great, don't really notice any slow downs related to temps, other then fish slow down in the colder months.

 

[snorvich]

Higher temperatures mean less dissolved oxygen.

 

[Eastone]

When I lived in Dubai, I used to regularly collect Acropora and a plethora of LPS that lived in water that would hit 40+ celsius.
As long as the temperature variance itself is stable, corals can and will adapt.

 

[figuerres]

one thing to keep in mind is that the reefs in the ocean had a huge mass of water that is always moving so a surface temp and the water temp where the coral is are not always the same and surges of deeper cooler water wash over the reef.

some areas have more swing between high and low and the corals in that area have adapted to that.

but it is true that most corals are evolved to only handle so much in the way of temp, ph and so on.
the trend of global warming is a problem when it moves the average temp to far to fast for the corals to cope with.

a tank that stays at 84 while it can be done I would treat that as a max temp and aim for 78 is a normal temp.

 

[HefeWeizen]

I ran my tank 82-84 for years when I had halides. Tank did fine. I think stability is more important IMO/IME.

Ron Shimek had a piece on world Coral temps and they flourished in areas where the temps were 80-86 degrees.

 

[Ron Reefman]

There are corals (zoas, softies, gorgonians and sps) that grow in the shallows near shore 'reef flats' that get up close to 90F in the Keys in the summer. They seem to be much happier then than in the winter (OK than in Dec or Jan) when the water temps are in the mid 70F.

I know these aren't the corals that were in your tank and they aren't the same as most of the big reef corals in the Keys or the South Pacific, but they are corals and they do well at 90F.

 

[MaccaPopEye]

The water temperature (not air temperature) of natural reefs in northern Australia range anywhere between 75F and 95F depending on where you are and time of year (roughly converted from Celsius as I don't really use Fahrenheit). Sometimes they can even go through almost that whole temp range in a single day.

I'm still new to this hobby so I try not to recommend that anyone else to do the same as I do however I run my tank at 83-84. I have a fair few LPS that are doing fine and am just now trying some SPS. To save on power my chiller turns on at 85 and will usually be on all day if I'm not home with the air-conditioning going. When I first started the hobby I did weeks of research into just temperature alone to make sure I wasn't putting my fish and coral at risk. I found that in our hobby it seems anything up to 85F is fine as long as there isn't a sudden change. There was even one reefer I found who had a successful mixed reef tank which had been running for a couple of years at 87.5F!!

The main risk I could find with hotter water is there is lower oxygen retention so in the event of a power outage your water will lose oxygen faster than colder water would so a battery backup or emergency air stones are recommended.

Cheers,

Macca