Intentional Temperature Swings & Fish?

[ISpeakForTheSeas]

Hey everyone! Long post ahead with questions that I'm curious about but understand we might not have any solid answers for just yet in the hobby. I apologize in advance.

So, I've been learning a bit about natural ocean temps that various fish live in and comparing that to the temperatures most aquarists keep their tanks at, and it has left me with a couple of questions that I'm looking for input on from some more experienced aquarists.

First, would intentional daily temperature swings (such as 78-74 F, 80-73 F or 82-72 F) to mimic natural daily temperature cycles have a negative effect on livestock (Fish, inverts, corals, etc.) in a tank? If so, why? If not, how extreme could they be before they begin having negative effects on the average reef tank? (i.e. would a temp swing from 78-74 F be okay, but a swing from 82-72 F cause problems? What about from 80-50 F as an extreme example?)

Second, would slow temperature changes over a long period of time to better mimic natural seasonal patterns cause problems in aquaria, and if so, why? (For example, would it be beneficial or problematic or just neutral to slowly lower the temp in an aquarium from 80 F daily to 76 F daily [or something like that] to mimic going from summer to fall?) *[I know with goldfish, for example, the fish digest food differently at different temperatures, so you need to adjust your feeding schedule to account for different temperatures. Would something like this be the case for marine fish as well or not?]

Third, I know it was mentioned in the breeding of certain sea urchin species (I think it was Tuxedo Urchins) that temperature "shock" was a key to inducing spawning in the urchins. What are some other species where this does or may apply? Would this be a sudden drastic change in temperature, or would it be a slower, steadier change?

Fourth and last, if it is safe/beneficial to let the daily temperatures fluctuate, would fish species that are considered cold-water (such as flashlight fish, for example) be able to thrive in a setup utilizing those temperature fluctuations? (i.e. would cold-water/nocturnal "cold-water" fish that usually struggle in normal reef tanks be able to thrive in a tank with daily temperature swings that takes the nighttime temperature back down to or even slightly below their recommended aquarium temperatures? For flashlight fish, pineapple/pinecone fish, and other bioluminescent species, would these temperature swings have a negative or positive impact on their bioluminescent bacteria species?)
*[I know flashlight fish can suffer and their bacteria can die off if they are kept at too high of temperatures for extended durations, but would a brief or even moderate length of time above the recommended temperatures have a noticeable impact?]

 

[HuduVudu]

First, would intentional daily temperature swings (such as 78-74 F, 80-73 F or 82-72 F) to mimic natural daily temperature cycles have a negative effect on livestock (Fish, inverts, corals, etc.) in a tank? If so, why? If not, how extreme could they be before they begin having negative effects on the average reef tank? (i.e. would a temp swing from 78-74 F be okay, but a swing from 82-72 F cause problems? What about from 80-50 F as an extreme example?)

I have for many many years set my tank to 78F and worked hard to keep it there. When I moved into my house I had to kind of let go of that, because of poor insulation. So I let the temps climb in the summer.

I finally asked myself why I was working so hard to keep such a stable temp when I absolutely know from diving that the ocean is not like this. My conclusion is that over the years I have tried to eliminate temp as a variable in deal with fish disease. It is an easy variable to eliminate. I don't have those problems any more (too a very very diminished extent). So I see my control of the temperature to be a vestige of the past.

Now I let the temp ride and cap it at the top and the bottom. I see a degree or so move a day. This doesn't seem to be a real problem. I think larger swings would be a problem. Though you could slowly introduce them IMO if you want and it wouldn't be a problem. Just make sure like everything in this hobby DON'T MOVE FAST.

Second, would slow temperature changes over a long period of time to better mimic natural seasonal patterns cause problems in aquaria, and if so, why? (For example, would it be beneficial or problematic or just neutral to slowly lower the temp in an aquarium from 80 F daily to 76 F daily [or something like that] to mimic going from summer to fall?) *[I know with goldfish, for example, the fish digest food differently at different temperatures, so you need to adjust your feeding schedule to account for different temperatures. Would something like this be the case for marine fish as well or not?]

In the reef areas usually the temp of the water is controlled by the tides. These changes can be quite dramatic and they don't really follow what we think of as seasons. This is my observation from my time living near a reef.

That said I let my tank ride witht the temperatures that you and I are accostomed to. My thinking is that this gives the fish at least something so that they are more used to temperature movements. So in the winter the tank runs cooler and in the summer the tank runs hotter.

Third, I know it was mentioned in the breeding of certain sea urchin species (I think it was Tuxedo Urchins) that temperature "shock" was a key to inducing spawning in the urchins. What are some other species where this does or may apply? Would this be a sudden drastic change in temperature, or would it be a slower, steadier change?

I have indeed seen Tuxedos do this, it comes from a drastic change. Once again, this is because in the ocean temperature changes can happen quickly. I wouldn't subject my tank to this because I am sceerd.

It is hard to experiment when things are working and you have a lot on the line if you make a mistake. That doesn't make it right it just means that for me I have a lot on the line.

Fourth and last, if it is safe/beneficial to let the daily temperatures fluctuate, would fish species that are considered cold-water (such as flashlight fish, for example) be able to thrive in a setup utilizing those temperature fluctuations? (i.e. would cold-water/nocturnal "cold-water" fish that usually struggle in normal reef tanks be able to thrive in a tank with daily temperature swings that takes the nighttime temperature back down to or even slightly below their recommended aquarium temperatures? For flashlight fish, pineapple/pinecone fish, and other bioluminescent species, would these temperature swings have a negative or positive impact on their bioluminescent bacteria species?)
*[I know flashlight fish can suffer and their bacteria can die off if they are kept at too high of temperatures for extended durations, but would a brief or even moderate length of time above the recommended temperatures have a noticeable impact?]

Cold water fish are cold water fish. In the tropics you don't need wet suits in Cali you need them at the VERY minimum.

I had a tank that had biolumincent bacteria, it ran at 78F.

 

[ISpeakForTheSeas]

Thanks for the reply! Lots of good information there. I'll be sure to do some more research on the temperature changing with the tides.

I don't blame you at all for not wanting to experiment with your tank's temperature to find out how far it can go without problems - that would be some risky business with a low potential gain and lots of potential loss. Would you have a guess though, as to how far it could fluctuate without issues? (If not, that's totally fine, you've provided a ton of good info already.)

With regards to the "cold-water" fish, I should have been a bit clearer there. I was meaning more like Anomalops katoptron (A.K.A. the Splitfin Flashlightfish), which is native to the tropical waters of the Indo-Pacific. They are recommended to be kept at lower temperatures than most fish from the Indo-Pacific (Jay Hemdal mentions in his article about them that their bioluminescent lights seem to do best around 72F to 74F, and that they may begin to lose their lights if kept at temps above 80F). Similarly, Monocentris japonica (A.K.A. the Japanese Pineapplefish/Pinecone Fish) is from the tropical Indo-Pacific, but it is also recommended to be kept at cooler temps (I've seen some people even recommend going as low 60F for them). With these and similar "cold-water" fish that normally struggle in the average reef tank, would they fare better in a tank that fluctuates from warmer to cooler, or would they still be better off in a strictly "cold-water" tank?

 

[PatW]

I am a scuba diver and I have dived in a large number of places in the Caribbean.

Daily temperature swings on the reefs are pretty minimal. If I am on the reef in the early morning, I get the same temperature in the late afternoon. The sunlight just cannot affect a large mass of water that much in that short of a time.

Annual changes on the reefs can be fairly large. Before climate change, reefs in the Caribbean pretty much peaked out in the low eighties in the late summer or early fall and hit their low point in the late winter or early spring in the low to mid seventies.

Also, on walls that are adjacent to currents, a shift in the current can bring up cold water from the depths and really drop the temperature in a few days and maybe faster. I went down to dive Jupiter in South Florida in August. I did not even check the water temps because Jupiter tends to be in the low eighties in August. But the Gulf Stream had brought deep water over the reefs and the water temp was 68 degrees. Since I was diving in a skin, I got really cold.

And some years ago when Florida still saw temperature snaps, the Keys saw water temps in the low sixties.

Generally, corals do OK as long as you don’t get over 84 degrees. And most things do fine on anything over 70 degrees. Just do not allow temperatures to change quickly.

 

[ISpeakForTheSeas]

Good to know.
So, the fastest "safe" temperature drop/increase would be something like a few degrees over a few days then? (Something like 78F to 72F in three or four days? or more like 78F to 72F in two weeks?)

 

[HuduVudu]

Would you have a guess though, as to how far it could fluctuate without issues?

Hmmm ...

I run from 74ish to 83ish. These are hard stops for me. Possibly the lower number could go lower. My fish have seen 68 because of the Texas freeze. This wasn't really good for them. If I had them longer it would have been less stressful. To that point I wasn't varying the temp at that time. I think now they would fare much better at that temp. Above 83 you start to run into gas exchange issues IMO.

I wouldn't move much more than a couple of degrees a day. It is possible to do more I suppose but that is where I start to get uncomfortable. Like @PatW said the upwellings can bring some really cold water. It is hard to get a good feel for what the reef is doing if you are a rec diver because you are only on the reef when the water is clear which is kind of shocking for the uninitated that the time available to dive is very short. Commercial divers would have a better idea but they are often not near the reefs.

With regards to the "cold-water" fish, I should have been a bit clearer there. I was meaning more like Anomalops katoptron (A.K.A. the Splitfin Flashlightfish), which is native to the tropical waters of the Indo-Pacific. They are recommended to be kept at lower temperatures than most fish from the Indo-Pacific (Jay Hemdal mentions in his article about them that their bioluminescent lights seem to do best around 72F to 74F, and that they may begin to lose their lights if kept at temps above 80F). Similarly, Monocentris japonica (A.K.A. the Japanese Pineapplefish/Pinecone Fish) is from the tropical Indo-Pacific, but it is also recommended to be kept at cooler temps (I've seen some people even recommend going as low 60F for them). With these and similar "cold-water" fish that normally struggle in the average reef tank, would they fare better in a tank that fluctuates from warmer to cooler, or would they still be better off in a strictly "cold-water" tank?

My guess to the reason these fish need cooler temperatures is because they come from deeper water. My educated guess about that water is that the temperature is more stable there. So flexing down to meet that IMO won't work. I definitely can be wrong here, just my opinion.

 

[ISpeakForTheSeas]

Again, great info, and that makes sense to me with the deeper water.

Thank you guys for the replies! I learned a lot of good stuff there.