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View Full Version : "Perfectly" stable temp or slight oscillation?


sfsuphysics
12/12/2008, 06:47 PM
So I hooked up my system to monitor temperature round the clock at 5 minute intervals (I know might be overkill), I tossed on my tank a single 500w titanium heater and noticed that my temperature would max out at about 78F when all my lights are on and drop to a minimum of 76.4 or so at night, making a little hot cold swing, very little swing...

well the other day I tossed in a 200w heater when I saw my temp drop below 74... found out my probe simply came out of the water slightly, but regardless since the temperature has wiggled between 78.4 and 78.0 round the clock.

So I'm curious what sort of day/night temperature fluctuations does the ocean get? I know the surface might have them to a certain degree, but what about a bit deeper? Should I keep with the more stable temp?

Skipper
12/12/2008, 09:17 PM
[moved]

Toddrtrex
12/12/2008, 10:18 PM
Greenbean has done studies on this.

I am sure my numbers are off a bit, but it was something like 78-84 over a 24 hour period.

For my tanks, they go from 78.5 to 82 each day, have been that way for years -- tanks are looking great.

IMO/IME fluctuations in temp allow the fish/inverts/corals to handled spikes when/if they happen. A while ago I was cleaning the sump, and my temp probe came out of the water. By the time I realized it the tanks temp was just under 90 (( it was a cool fall day, and the windows were open )). It had been at least 6 hours that the probe was out of the water. Notice zero ill effects from it.

Playa-1
12/12/2008, 10:31 PM
My temp will swing about 3 or 4 degrees on the average day.

reefworm
12/12/2008, 11:01 PM
you're fine with variations of 78~86. Mine runs between 80~84 or so.
Here's the thread Toddrtrex is referring to:
http://www.reefcentral.com/forums/showthread.php?threadid=1525963

sfsuphysics
12/13/2008, 12:23 AM
Thank you, that was a good read, and I see it was quite recent too.

Don't quite know if it'd make much of a difference to have a 1.5 degree swing vs a 0.5 degree swing as far as "tempering my corals against a big drop.

It would seem to me that it's more energy efficient to let it get a bit cooler, but then it's been a long time since I took thermodynamics so I don't quite have the info at the top of my head whether it takes less energy to keep a body warm than to let it cool then warm back up since it is two separate mechanism that are cooling thermal transfer (i.e tank is colder than surrounding air, therefore heat exchange occurs) and evaporation. Of course knowing how much energy of each one most likely will be key.

End result, since it's apparent my 500w heater can't keep the tank temperature stable by itself, a lower ambient temp would mean it'd drop even more, so perhaps I'll simple let my controller kick the second heater on when it's much lower.

reefworm
12/13/2008, 09:06 AM
That sounds like a reasonable approach. I'd try to get your mean up a bit higher than 78ish - maybe the 80~81 neighborhood. In any event you're in a good range as is with 78[the 74 was a bit low]. Just keep an eye on the animals' reactions. IMO you needn't worry about it as long as you stay more or less where you are.

sfsuphysics
12/13/2008, 10:19 AM
See I always thought people over heated their tanks with the 80-83 range, I used to be of that mindset but recently decided the 77-78 range was a bit better. Now I have no evidence or sources I can site, but I recall reading something a while back... and I'll just leave it at that ;)

The 74 thing wasn't a tank temperature, it was a "user malfunction" when the probe was partially out of the water, as a result it was reading a few degrees lower than norm.

reefworm
12/13/2008, 10:21 AM
got it. you'll be fine with that. :)