# Thermometer Recommendations?



## CITADELGRAD87 (Mar 26, 2003)

I always ran a little time and temp until I got a chiller that gave me real time temperature readout.

I recently bought another little time or temp, and it seems to give poor readings, 73.9 just now despite the water feeling warm to the touch, my guesstimate is 79-83 range. Last time I had it on this tank, it read 82, and I tend to beleive that temp, this is the tank that runs warm and used to have the chiller.

I tried one of those garbage stick on ones, it doesn't display any temperature.

I've read the reviews, I think I gave the L t and T a good review 7 years ago.

Anyone have any recent experience on a thermometer that you could recommend or advise me to stay away from?

Thanks


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## PfunMo (Jul 30, 2009)

I've tried various types and always come back to the simple glass type. Digital is sometimes great but I find they tend to drift as the battery goes lower. I was never sure the stickon was reading the water temperature or the air outside the tank. It was often different than thermometers inside. I hate suction cups as they get dry but they seem to give the best choice of where to put the thermometer. Still looking for "perfect"!


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## CichMomma (Mar 3, 2010)

I gave up trying to find a perfect thermometer. On my largest tank I have a digital and a stick on (it was already there), on my planted tank and my fluval chi I have a stick on, and on my 20L I have a hanging glass therm that came with the tank. I have never had any problems with the stick ons......I kind of like them actually. Of all three, however, I prefer the digital.


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## rich_t (Nov 26, 2009)

I have never cared for those stick on types.

I found them to be inaccurate. I use a basic glass type, with a suction cup to hold it in place.


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## vann59 (Jun 20, 2011)

I find the with stick on ones, you need a flashlight to read them. I live in Florida so it's normally not a problem since the tank stays at my room temp. But now it's cooler, and I have to warm the tank, and I'm treating Ich, so I put in my new Fluval E 300w heater. I really like it, it accurately heats and the readout is illuminated, so I can finally read the temp easily.


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## rich_t (Nov 26, 2009)

vann59 said:


> I find the with stick on ones, you need a flashlight to read them. I live in Florida so it's normally not a problem since the tank stays at my room temp. But now it's cooler, and I have to warm the tank, and I'm treating Ich, so I put in my new Fluval E 300w heater. I really like it, it accurately heats and the readout is illuminated, so I can finally read the temp easily.


Are you comfortable with the temp gauge being built into the heater?

I've always kept my thermometer as far away from the heaters as possible.


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## Alpha7 (Apr 27, 2011)

Quality is a major factor with digital thermometers: Some of the cheaper ones will lose accuracy with low battery power, some may not be accurate at all right out of the box. Better ones simply shut off when the battery is to low to be accurate, and some have an auto-calibrate feature.

When I say 'cheaper', I mean anything under $15 or so. Just to be clear: I am not saying you shouldn't buy one... just make sure you have something to verify it by and make sure it stays calibrated:

I usually put a stick-on ($5) in a hidden location, and then use a cheap digital ($10) for regular monitoring. The heater should theoretically keep in range of what it's set to. If the digital starts to wander outside of the proper range I just check the stick-on real quick to see if it agrees. If so, check the heater. If not, get a new battery/thermometer!

Something as simple as the 'top fin' or 'exo-terra' digital thermometer works fine, and the probe is designed for aquariums. I stick to the $10 range because the battery alone is $4, so whether it's the battery or the thermostat itself thats dead, it's still cheap to replace.

As far as other thermometer types go, I have a little pro/con list:

I find the older heaters with mechanical thermostats tend to drift over time. Newer digital models seem to be much more precise. Tank placement is moot: because it is a heater, the area around it will be the same or slightly warmer than the rest of the tank, thereby limiting accuracy to a degree. An exception to this being filter inlet heaters, which heat the flow of water going to the filter (what I use in my 120g).

The stick-ons are actually quite accurate, as they are thermoreactive crystals. The layer of glass however, slows reaction time. They aren't exactly easy to read either. Tank placement is also limited to the outer glass surface where water is, and they aren't exactly eye-candy. They also don't work so well if you try to remove & reapply them. 

The glass bulb filled with alcohol (or mercery) is very accurate and needs no calibration. Aside from obviously being breakable, it is also slow to react. Tank placement typically leaves you measuring the top of the tank, and it's visible like the stickon.

Digital thermometers are very accurate, quicker to respond, most do not require calibration, and they allow for a remote probe to be placed in optimum locations within the tank. The probe must be waterproof however, and non-corrosive.


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## skurj (Oct 30, 2011)

I had a stick on on my tank, for a few days. I had the heater set as high as it would go and the stick on said it was 80 deg in the tank. I tried a glass and a digital, they both said the actual temp in the tank was 86 deg...

The stick on went in the garbage then and there.


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## prov356 (Sep 20, 2006)

I use stick-ons, but rarely look at them. I touch the water to see if it feels too hot or too cold and move on. Fish are fine in a pretty wide range. I just don't see spending big $$ on digitals for some 30 tanks. Whether it's 79 or 82 in the tank just doesn't matter, IME. Stick-ons go with my approach, I guess, better than some who look for precision.


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## PfunMo (Jul 30, 2009)

Some of the attitude about precise temperature is an unforutnate result of the marketing done by many dealers. If we check the advice from some of the sponsers of this site, you can find an example. It is often a far larger concern to sell more and more expensive equipment rather than give good honest advise. That makes many people believe that temperature is to be held within a few degrees of a special point.

This is an example:


> since value heaters may cause the temperature to drop more than one degree per day, causing much unwanted stress.


Look at a lake and ask what the temperature does. Obviously fish will move to different parts of the lake as the temperature changes but that doesn't mean they get there without passing through different temperatures and stay there. As they move in and out with the seasons, they also move in and out to feed and do their normal activities. It is folly to believe that fish live their entire life at a steady temperature. Does the temperature at lake's edge not change when the rains come and the rivers flood? Does a shallow fish pond in Florida never change temperature from summer to winter? Nature is not that steady nor precise! Keeping the temperature somewhat steady is good but not something to stress over!

Selling equipment is what dealers do, so check any information they pass out. Run things through the old head before passing out the big bucks!!!


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## prov356 (Sep 20, 2006)

I agree, all heaters allow 1 degree of change or so, and if more caused a lot of stress, my fish would have all been dead long ago. There does seem to be some concern about keeeping precise temps by some. My attitude about it is pretty casual, but I just haven't seen the need to be more concerned.


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## cantrell00 (Oct 30, 2010)

prov356 said:


> I agree, all heaters allow 1 degree of change or so, and if more caused a lot of stress, my fish would have all been dead long ago. There does seem to be some concern about keeeping precise temps by some. My attitude about it is pretty casual, but I just haven't seen the need to be more concerned.


I agree... I think the stress is caused by quick shifts of 8-10 degrees. If the changes are gradual, I don't think it matters much.


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## CITADELGRAD87 (Mar 26, 2003)

I agree with the above. I have always used the fingertip method to match fill water with tank water, I checked it a couple times and I was about a degree off max, since I have so much water movement, it's distributed very rapidly in my tank. Our pediatrician told my wife that human touch is more reliable than a thermometer for low fevers.

My reason for wanting a good thermometer is I am days away from firing up my 100G in wall monstrosity, and I am going to fishless cycle it. Every single thing in that tank will be new to me equipment, and I would like to be able to verify temps that I will elevate for cycling, and later drop them for the fish. I have a finnex heater and controller, not sure where to put it in the sump for max effectiveness, etc. I also need to know how long it will take to heat up 40G of sump water during water changes. I don't know how high up to turn it to get it where I want, or how long a big tank takes to heat up or cool down. For all this, I wanted to have a "go-to" that I can trust to tell me tank temperature, at least until I figure out the tank's personality.

Personally, I have basically let the 50G go on autopilot for years, it had a good hydor in line heater and a chiller, I could not have cooked the fish if I wanted to. My water was within 2 degrees for over 5 years, no matter what the room was doing.

I bought the little T and T for the new tank, and also figured I could rapidly move it from one to another tank spot checking, one 10G grow out is in the garage and winter is coming, even here in SouCal, one's in the laundry room, and the big one is gong in in the wall.

For 3 weeks, the 50G was reading at 82 degrees, I checked it a lot because I pulled the chiller off now that it does not sit in my office over the un air conditioned weekends, and I was worried my pump would slowly elevate the temps. I actually decided that the chiller heated the tank indirectly, it was in the enclosed laundry room, and the hot air from the chiller heated the room so much that the tank heated up from that. The electric company was sad I fugured out that little tug of war.

This weekend, I put the probe in to 50G as I started a water change, but it never got above 73.9 degrees, pretty far under the 77 that I shoot for as a minimum, but the water felt as warm as when it said 82. I will swap out the battery, but I was pretty certain the temp was way wrong.

That's the reason for the question, thanks for all the input here, some really great info as always.


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## DanniGirl (Jan 25, 2007)

*CITADELGRAD87*,

I highly recommend this digital thermometer: A150QCERT Min/Max Digital Thermometer with High/Low Alarm and Long Form Certification

It's efficient and works well. I've been using them for a while and they were recommended to me from one this site's sponsors.

As for running heaters, I never use them. I have them, but like the above posters, minor fluctuations in the water temperature will not cause stress to the fish. The thermometer is more of a safety net for when a "non-fish" person is watching the tank.


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## cantrell00 (Oct 30, 2010)

> As for running heaters, I never use them. I have them, but like the above posters, minor fluctuations in the water temperature will not cause stress to the fish. The thermometer is more of a safety net for when a "non-fish" person is watching the tank.


This is a very good point that I didn't consider.

I don't use heaters either. Assuming you keep your house temp somewhere between 68-75 degrees, heaters can actually present more of a hazard than a aid... Particularly on tanks larger than 100 gallons.


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## CITADELGRAD87 (Mar 26, 2003)

I have a heater and am not sure I need it. This will be a 100G with a 60 gallon capacity sump, I figure 90 gallons in the main tank and probably 40 in the sump, 130 total gallons roughly. I will be running a Mag 24 pump for all circulation duties, and I know that is going to throw some heat. The tank will be located in a dead space between the living room and family room, and I am not sure what the ambient temp will in that area, only a single long side will be "in" an inhabited room.

Because I don't know how the tank is going to run, I bought a 300W finnex and separate controller, if the tank stays warm enough this winter without it, fine, but I really cannot say what the tank is going to do with just the pump. Either way, 300W is undersized for the water volume, so I am not too worried about a runaway heater.

I have my bases covered, I have a contingency plan to run a chiller exhausted to the crawl space if the heat buildup goes unchecked.


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## DanniGirl (Jan 25, 2007)

cantrell00 said:


> This is a very good point that I didn't consider.
> 
> I don't use heaters either. Assuming you keep your house temp somewhere between 68-75 degrees, heaters can actually present more of a hazard than a aid... Particularly on tanks larger than 100 gallons.


Yes, how true. The 150 gal. tank seldom fluctuates beyond a couple degrees.
In the winter, it may drop a little because we're not always in that family room, but it's nothing to cause concern.


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## PfunMo (Jul 30, 2009)

A big factor not often mentioned when reading about heaters is the size of tank. Big tanks are just much easier to keep steady on most points. A small tank heater is needed far more often than on a big tank. A big tank will settle on pretty close to the room temp and stay there unless there is a major change. You can do a 25 % water change and not notice the difference. If you do a 25% on a ten gallon and the new water is off by ten degrees, you will often see a change in the small tank temperature. I watch the temperature on my small tanks much more than my mid and large tanks.


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## vann59 (Jun 20, 2011)

rich_t said:


> vann59 said:
> 
> 
> > I find the with stick on ones, you need a flashlight to read them. I live in Florida so it's normally not a problem since the tank stays at my room temp. But now it's cooler, and I have to warm the tank, and I'm treating Ich, so I put in my new Fluval E 300w heater. I really like it, it accurately heats and the readout is illuminated, so I can finally read the temp easily.
> ...


I do like having a visual reference, and a visual warning, if the temperature varies significantly. The specific spot temperature isn't going to vary much in a tank with reasonable circulation. The other thing I wanted in this heater is a digital control so that it will kick off rather than get stuck on and kill the fish by overheating. Here in Florida heating is only a seasonal thing anyway, and I'm treating ich at the moment, so I do want the higher temp, but I want to be safe as well. But I have to say that the old finger test is enough most of the time.


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