Temperature fluctuations

[Kendra]

Hello. I am just setting up a tank now, and I am having some trouble getting my temperature readings to stay constant.

 

I have an AGA 7-gallon bowfront. The lighting right now is the cheapy 40-watt flourescent that came with it. I have a 75 watt Ebo Jager heater, a Rio 50 powerhead, and a penguin biowheel "mini" running in the tank at this time. I also have a digital thermometer with a sensor in the tank giving me readings ("Lifegard little time or temp"). There is nothing in the tank at present, but 8 lbs of nice live rock from premium aquatics, as well as 3 lbs of live sand, are supposed to be arriving Wednesday. I have seawater mixed and circulating in the tank. My tank is located against an inner wall, and gets sun on it only in the evening. There is no heating unit near it. My apartment is upstairs, and thus is generally about 75-80 degrees from the ambient heat from other people's apartments. I rarely have to turn the heat on.

 

Here are the problems I am having.

 

First, the tank tends to get too hot (82 degrees is the highest I have noticed).

 

Second, the heater and the thermometer do not seem to agree on what temperature it is in the tank. I found the heater actively heating when it was set to 75 degrees and the thermometer showed the temperature as 80 degrees. To clarify, the heater is set up where there is a little cut out for it in my tank cover (about 1 in from left side of tank), and the thermometer sensor is about one inch in from the right side of the tank and about 2 in from the bottom. The very bottom of the heater is at about the same height as the thermometer sensor, so they seem to me to be in reasonably equivalent positions. The Rio 50 is stuck to the wall right next to the heater, with the little bend attachment in place directing the current across my tank and away from the heater. On the other side of the tank, the biowheel intake is about 2 in from the thermometer. All of this may not mean anything, but I am hoping that the reason for the discrepancy between the two pieces of equipment has something to do with faulty tank placement and that someone will correct me. If one of the pieces of equipment is just miscalibrated, which one is it more likely to be?

 

What I have tried so far to rectify the situation:

 

Putting a couple of chopsticks under the light strip to give it more circulation. This had no noticable effect.

 

Turning the heater down to 73 degrees. This does seem to work somewhat, but I am having trouble with fluctuations of temperature now.

 

Perching a tiny fan on top of the biowheel, aimed at the light strip. This works all right, but is not very elegant. Still trouble with fluctuations. Also, I am having mad evaporation, about a pint daily. I do have a doser coming that I could rig to combat that effect, but it still seems awfully high. My temperature variance is now between 78 degrees at highest to 74 degrees at lowest. Also, I am worried about what will happen when I upgrade my lighting. I am eyeing 32 watt x2 CFL, when I can afford it. Will that produce more or less heat than my current set up? If more, how can I rig it to cope?

 

How much daily temperature fluctuation do people normally have? How much is acceptable? Does anyone have any better ideas than my jury-rigs? Should I return the heater, or just spend the time to figure out exactly the variance in temperature from my heater? Do I need to get a second thermometer to double check the first?

 

I realize this post has grown larger than it ought. Thanks for your patience and any advice.

 

Kendra

[printerdown01]

WOW! I don't have a clue. Try a couple of things though: a) Try a second thermometer to make sure the first isn't jumping all over the place. Try a different heater if you have one. Ebos are supposed to be extreamly reliable, BUT there is always a possibility of having a bad apple! Also make sure you have a place for heat to escape at the top of your tank. This will also help with 02 exchange. I don't know what else to tell you, excpet I'm sorry that you are having to go through this!

-Anthony

p.s. as for what people normally shoot for: no more than 2 or 3 degrees in flux!! A flux this much is going to cause serious stress in the tank.

[glazer]

I gave up typing earlier... I'm too tired and it started gettin' all wacky...lol Sooooo, I just deleted everything and when I came back I see printer answered ya...good!

 

Go to the medicine cabinet and get the thermometer out and check it against the digital one in the tank... my bet is the Ebo is way more accurate than the digi temp thingie. Get the Ebo dialed in... if the temp is still flucuating alot then take the heater back. I would shoot for a solid 80 in the tank based on your ambient room temp.

[Kendra]

Thanks for the replies, Printerdown & Glazer. Hmm. . . I have one of those little adhesive thermometers. . . I think I'll attach it, though it too could be inaccurate (seeing as how I got it free. . .) Other than that, I think I'm going to try swapping the positions of the sensor and the heater and see if anything changes. I'm glad to hear that a stable 80 degrees would be OK- I've been trying to force the readings down to 75 degrees with that fan, with variable success as reported. I think I'll turn the fan off, since it seems to be a major culprit in the fluxes. If it's still too hot, maybe running it to the timer with the lights, so it only comes on when they do, would help. By the by. . . what is the max acceptable temp for a nano? The book I have been consulting the most, Natural Reef Aquariums by John Tullock, gives a desired range of 73-78, but says that "natural" range is about 68-84. Wasn't quite sure what to make of that. . . Any opinions?

Thanks, Kendra