Can't get water temp to 78 degrees

[Stef]

Hi folks, I'm trying to heat my 20 gal long to at least 78 F degrees and can't quite get there.  I'm topping out at 74 F degrees.  The tank has no lid yet, though I've tried partially covering it with another spare glass lid from a smaller tank which covers half of the 20 gal.  I've also got two heaters in there now (one is a 100 watt compact pre set from Tetra, the other is a 50 watt from Fluval that is set to 82.  I've also got two different floating thermometers in there as I thought one I originally had in might have been old or stuck.  Both register 74 degrees. Each thermometer is on opposite ends of the tank. The heaters are positioned vertically and are evenly spaced in the back. 

I plan to keep it lightly stocked with a female betta, panda corys, a BN pleco, and some small schooling fish like Embers or CPDs.  The tank has been set up for 7 days and has two fully seeded filters (coop medium sponge and a small Dymax Slim Flo).  No fish are in the tank yet but wanted to get my betta in there along with my corys from two different tanks I'm consolidating and to keep the cycle going. I've been feeding the empty tank every other day with a small pinch of flake food or a few betta pellets.  I know the corys can take the cooler temp, so maybe I should start with putting them in first and/or the BN pleco first?  They'll be harder to catch. 

My heat (in the house) is set to 68 and I don't want to increase that.  Will it be impossible to get to 78 or do I need a 200 watt heater? Or give up the idea of having a betta in there?

Appreciate all comments. Thank you.

[Katherine]

I would start by testing each heater on it's own in a small bucket of water. See if both are capable of heating to the temp you need in a smaller volume. One or both could be busted. If that checks out I'd probably replace the 50 watt with a larger one if you can afford to.

[DaveO]

I have one 100 watt heater in a 32 gallon and it heats it to 78° with no problem. I do keep the house warmer though. You probably need to run two 100 watt heaters in yours.

[Cory]

I think a proper fitting lid is the answer here. Also with the hang on back filter falling into the tank, it's doing evaporative cooling. I'm not a fan of rimless tanks without lids for these reasons as they are a pain to keep temp. In a pinch you could try saran wrap to see if that fixes the escaping heat problem.

[Patrick_G]

I'd double-check the 100w in a bucket and see if you get to 78F like @Katherine suggested. I've owned a heater that was defective and the tank wouldn't get above a certain temp. That might be the problem here

[Stef]

Thanks for all the tips. My 100 watt is a compact version as the tank is not tall, though I could try horizontal. I definitely want a lid but it’s been out of stock, so will custom order a from a glass shop that’s nearby. I like the Saran wrap idea. Will condensation pull it into the tank?  Will try it anyway as I have a ton of it. 
 

You all are the best!!

[Widgets]

Are the heaters staying on continuously? If so, it is a sign that there is too much heat loss. You would need to decrease the losses with a lid and a higher water level, like Cory suggested. 

If the heaters are cycling off, it may be that the temperature control for the heaters are poorly calibrated. You could set them higher and see if the tank temperature increases.

For the horizontal orientation to make a difference there would have to be water flow issue, the heated tank water rises up to the control sensor and shuts the heater off before the tank gets up to temperature. That both sides of the tank read the same temperature,  this is not likely the problem. You could move a thermometer closer to the heater to see if it reads the same.

[Wrencher_Scott]

My guess is that 100 watt either doesn't work at all or is "set" to 74 or less. 

A cover will drastically reduce the evap so that's another plus besides holding heat.  

[nabokovfan87]

On 4/27/2022 at 4:48 PM, Stef said:

My heat (in the house) is set to 68 and I don't want to increase that.  Will it be impossible to get to 78 or do I need a 200 watt heater? Or give up the idea of having a betta in there?

Extremely common.

You just need to add multiple heaters.  Let's say your tank takes a heater of 150W (just saying a random number).  If you have the flow, you'd run multiple 150W heaters.  This also evens out the heat on the tank so you have less cold spots.  That being said, if you don't have enough flow, instead of running a larger more powerful heater, you can run multiple 100W heaters (again, random number).  This will help you get a bit higher temperatures and not be running the heaters at full bore 24/7. 

Most heaters will say in the manual what they can actually do. The only raise the temperature above ambient a certain amount of degrees. After that it should specify a suggestion on adding more heaters or more powerful heaters.

You're looking for something like:

This is from the M-Series heater you have running:
50W = 15G recommended tank size.
 

Quote

*HEATER PERFORMANCE VARIABLES
This heater was designed to reach and maintain the set temperature, provided that the maximum difference between
the ambient and set temperature is less than 10ºC (18ºF).
Variables such as lower room temperature, wide temperature fluctuations, lack of an aquarium cover, presence of
pumps and filters or aquarium placement in proximity to cooling sources may require a higher wattage for proper
control. If the set temperature is not reached in all conditions, it will probably be necessary to increase the heating
power.
We recommend monitoring aquarium temperature on a regular basis with an accurate thermometer such as the
Marina Aquarium Thermometers.

For the Tetra heater:
The manual does not specify what the ambient air temp is for their heaters.  I can assume it's a certain value, but we have no real idea if these are designed to be +5 degrees or what power of heater.  The wattage you're running is on par with everything said above. That being said, you can view the tetra website and it's about 75% of the reviews being "it didn't heat the tank above 74".

So perhaps there is just more to the story when it comes to those specific heaters and their set temperature calibration range.



This video, talks about the issue you're having, but it also has a few tidbits from a heater manufacturer about proper use.  It specifically breaks down use for pre-set heaters and some issues you might run into. Hopefully that helps!

 

Edited April 28, 2022 by nabokovfan87

[Andy's Fish Den]

I am not sure between the heaters that you are using that you have enough there. You may need to upgrade heater(s). With only having  the room temp at 68, you're wanting to bring the tank temp up basically 10*. The 100 watt preset one is only pre set to somewhere in the 74-76* range, and I would be willing to bet that it con not even hold that temp and is on continuously. They are generally only designed to bring the water temp up a few degrees above ambient. Then the little 50 gallon one is trying to make up all the extra needed heat, and is also on continuously. I would try putting saran wrap over the tank as well as raising the water level a bit so the HOB isn't splashing down into the tank. You will know if you have the top covered with the saran wrap if a larger lid will work, but my guess is that it still won't get it to the 78* that you want. 

[Stef]

Big thank you @nabokovfan87 and @Andy's Fish Den for such detailed tips and the video.  Both heaters were new out of the box and I admit I glaze over the manufacturer's instructions. After I saran wrapped the tank overnight, both thermometers were reading 76.  I did not know that heaters are generally only designed to bring the water temp up a few degrees above ambient.  Thanks again all, I have a better plan now.

 

[nabokovfan87]

On 4/28/2022 at 7:22 AM, Stef said:

Big thank you @nabokovfan87 and @Andy's Fish Den for such detailed tips and the video.  Both heaters were new out of the box and I admit I glaze over the manufacturer's instructions. After I saran wrapped the tank overnight, both thermometers were reading 76.  I did not know that heaters are generally only designed to bring the water temp up a few degrees above ambient.  Thanks again all, I have a better plan now.

Just guessing... the pre-sets are set for about +5 deg. you're running two of them which gets you from 68 up to around 72.  Because you have 2. 74-76.  Adding the fluval one, which is a +10 is probably doing a lot of the work.  I'd try to find a 150W (or two 100W) of the fluval ones if you can and pull the tetras.  Keep an eye on when the thermometers are active. They will have something that forces them to cool off after a set period of time as a safety mechanism.  That being said, if you're seeing them all or a lot of them running constantly, then it's likely the issue mentioned above entirely based on assumptions because we don't have those stats from tetra.

I'll be interested to see how much the lid helps, but, I also would just keep in mind that the thermometers (tetra) are very not likely designed for this load and the fluval one is under wattage for that load as well.

[Andy's Fish Den]

On 4/28/2022 at 10:22 AM, Stef said:

Big thank you @nabokovfan87 and @Andy's Fish Den for such detailed tips and the video.  Both heaters were new out of the box and I admit I glaze over the manufacturer's instructions. After I saran wrapped the tank overnight, both thermometers were reading 76.  I did not know that heaters are generally only designed to bring the water temp up a few degrees above ambient.  Thanks again all, I have a better plan now.

 

I learned this about heaters only being designed to bring tanks a few degrees above ambient by trial and eror and then heard it from a sales rep for a manufacturer. I had always had tanks in my living area, and kept thermostat at 72*, but with my house I moved into 10 years ago with a basement, I started putting some tanks down there and the first winter I couldn't keep the tanks warm, I finally had to have a 300 watt heater in a 29 gallon tank to even keep it around 75*. By the next winter, I had added heat ducts into the basement and insulated, and it was much better and I can easily keep tanks in the 80-86* range easily. 

[Widgets]

Cory to the rescue.

 

[Tanked]

I really haven't got anything new to contribute here, other than to say that talk about "a few degrees above ambient temperature"  plays with my head.  Regarding your heaters, just because the lights are on, doesn't mean they are working.   150 watts should be more than adequate.  I don't know if it was mentioned yet, but your heaters are probably playing against each other. I would try moving them as far apart as possible.

My ambient winter temperature is 60 degrees. My uncovered  29 gallon has one preset Aqueon 100 watt heater that maintains 76 degrees +-1, degree placed under the HOB. 

[Stef]

On 4/29/2022 at 10:14 AM, Tanked said:

My ambient winter temperature is 60 degrees. My uncovered  29 gallon has one preset Aqueon 100 watt heater that maintains 76 degrees +-1, degree placed under the HOB. 

Fascinating. I ended up buying an Aqueon 100 watt (not pre-set) and now have it and the Tetra 100 watt compact working together. Temp is up to 76 on one end and 78 on the other which is closest to the hob. I’m pretty happy about that. A day late on the coop heaters. Can’t wait to try it out soon. Custom glass lid should be ready today or Monday which will help even more. 

[Tanked]

On 4/30/2022 at 9:26 AM, Stef said:

Fascinating. I ended up buying an Aqueon 100 watt (not pre-set) and now have it and the Tetra 100 watt compact working together. Temp is up to 76 on one end and 78 on the other which is closest to the hob. I’m pretty happy about that. A day late on the coop heaters. Can’t wait to try it out soon. Custom glass lid should be ready today or Monday which will help even more. 

I'm glad you are getting closer to your goal.  My Aqueon is supposed to be my backup heater, so the ACO heater is just in time.  My HOB is actually side mounted, and pushes water across the length of the tank.  The addition of a small circulation pump may help if the lid doesn't do it for you.  

[ndcenterdiplomas]

If your current heaters aren't reaching the desired temperature, upgrading to a 200-watt heater should help, especially with a partially covered tank. Starting with the corys could work, as they can handle cooler temps. Ensure the heater is well-placed and consider fully covering the tank to retain heat.

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[mynameisnobody]

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