Temperature extremes on the reef
 

I recently moved my tank to a greenhouse outside. I'm in Dallas, TX and the weather can go from 35F to 85F on consecutive days. I was setting up this outdoor solar tank during some of those days and my Apex wasn't up and running properly for the first two days of the transfer. The tank is also remote so I can't access it without a 30 minute drive (it's complicated).

As a result, the tank went from 64F to 87F over a couple of days .... I expected everything to be dead - coral, fish, inverts. I was ready to basically go scrap it but I was shocked that everything was alive.

Well, the transfer was rough on a few of the weaker SPS, but that was the move not the temperature extremes...

so - does that surprise you? I was shocked. I think that real reefs do see such extremes, but they don't last very long. So a reef CAN handle such extremes, but only in short spurts?

Sharing and looking for feedback...

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more pics on the build thread:
http://www.reefcentral.com/forums/sh...2653824&page=4

Interestingly.. 64F is what NOOA shows as the lowest extreme for reefs in nature

https://oceanservice.noaa.gov/facts/coralwaters.html

The lowest air temperature in the barrier reef hit 63F (17C) in their winter (July), but it looks like the lowest measured water temperature was 73F (23C)... still, that could mean that the shallower areas could have been colder.

https://www.great-barrier-reef.com/g...f-weather.html

No surprise here. Real world Mother Nature is pretty amazing and weather shifts daily. Storms, clouds, rain, etc. You already know this but no, it doesn't surprise me in the least.

I just had an an eleance survive a shipping trip from aqua sd that was at 47F when it arrived.... Also some zoas every thing else I ordered died though .

Sent from my SM-G950U using Tapatalk

Mine is experiencing temperature swing between 26C up to 31C on daily basis (unless if it's raining), so far no issue (only one aussie acros didn't make it).

Here's another interesting observation...
I had been battling an unusually invasive form of encrusting bacteria in my tank. It all moved to the new tank with these extreme conditions... over the next few weeks, the bacterial growth has started to die off en-masse.

My theory is that occasional adversity can actually improve a biosystem's health by pruning off excess pathogens. The same goes for low tide events- the mucus produced sloughs off any persistent parasites and the corals can weather without issue.

I’m not overly suprized there were no deaths, but if your corals see those kind of temperature swings on a regular basis at a minimum I would expect them to not do well, most likely you will start to have die offs.

Stand in the shallow part of Hanauma Bay in Hawaii. The water is extremely warm, then very cold as a current comes in. Move around. The fish stay the same but the temperature varies drastically. The fish don't seem to notice and they don't stop eating.

My skin is not an accurate thermometer but I know what it feels like to me.

In tide pools on the same island when high tide fills it up the water is cold. As the day goes on the sun heats the water up a lot. There are corals and invertebrates that are active through both extremes.

Karim, what were the daily swings on your reef pre-move? I know it ran warm in the summer near the end of the photocycle, how cold at night?

Summer was 78-84F
Winter was 76-78F

There were a couple of days it dropped to 72 but not in the 60s.

It probably helps that the sun is heating the surface of corals

When my family and I snorkeled in ST Criox in late December back in 2012 the water temp was in the high 50's sometimes; other day's it would be mid 60*... Air temps never went below 70*.

??? I've never heard that coral can live in sub 60

With the arctic blast in full swing, the water temp hit the extreme low of 60.3F last night as the air temp went into the 20s.

I could have gone nuts and added on all my halides and bought 2KW more heaters (there's 3KW on there now), but I wanted to use this as a learning event (doubting anything will survive, but still....)

Another thread had this article that points to 16C being the extreme min on tropical reefs with low mortality (61F) and case at 11F with high mortality (52F)

http://journals.plos.org/plosone/art...l.pone.0023047

I haven't gone over to check yet.. temp is slowly rising again and is at 66F now.

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I'll share what I learn

Not surprised. I know from persoanl experience Purple Stylo will tolerate at least 50°. Unfortunately the use of the colloquial terms "SPS" and "LPS" as indicators of an animals husbandry requirements has led to many misperceptions about what a species/genotype will tolerate. Decades old assumptions about phosphate has also led to creating marginal conditions that makes corals very susceptable to changes in lighting and/or temperature.

https://www.researchgate.net/publica...s_to_bleaching
http://www.sciencedirect.com/science...25326X17301601

Consider covering the tub with something like a pink foam insulation sheet on those cold nights, should help a lot.

I agree. Some people advertise GFO and GFO reactors as something that needs to be used in all tanks 24/7. But imo GFO is one of those compounds that should only be used if you are battling extremely high phosphates (or extreme algae growth). And this should only happen in new tanks that the rock or sand leaches Phosphate. If you need to use GFO in a mature tank, you are either overfeeding or dont have enough filtration.

Most of the explainable issues with corals can be traced back to over reduction of phosphate and/or an unbalance of nitrate and phosphate (N/P unbalance, mainly high N but trace P, is something that is rarely discussed by, in my experience is one of the main suspects for SPS bleaching). All this is tanks to over-advertisement of GFO.

GFO even cause nitrates to increase because it cause P to become a limiting factor for bacterial growth. And since we dont have a media that can strip water of N like GFO does for P, it causes the high N, trace P situation I explained above.

My concern isn't that it dipped below 70. It's that it's a sustained chill in the 60s for several days now

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None of the fish are floating dead and the coral looks normal but I don't think we'll know until the temperature returns and they "thaw" out - that's where the biological crisis controls stop and damage shows up. Like having fingers and toes visible but frostbite will manifest afterwards.

Well, at this point it's a wait and see. You might see some problems in a week or a month. It would be very educational for all of us if you could post the corals you have, descriptions of how they look and pictures of the individual colonies (weekly would be nice :) ).

Cover with double-wall poly polycarbonate? https://www.homedepot.com/p/Sunlite-...2506/202091947

Pictures tomorrow. The largest green acro is bleached white.

Very sorry to hear that! :(