Best Heating Arrangement For 75g In Very Cold Room?

Bbunkie01

Hello, all.

I have a 75 gallon freshwater tank in my master bedroom. The room gets very cold at night, down to a consistent 62f from about midnight to 9-10am, at which point it'll go back up to around 70f for the rest of the day.

Right now I have a single Finnex 250w heater in the tank set to 77f. My separate thermometer in the tank consistently reads 75-76f. The heater is on basically 24/7, and it's a matter of time before it dies due to such constant use.

I would really like to install an inline heater on my Fluval 406. But I've heard a lot of mixed things about Hydor's inline heaters failing after only a few months. Their biggest model is a 300w. I'm afraid this would fail due to such extreme ambient cold in the room. We're talking about a 15f increase here.

I also see an ISTA brand inline 500w heater on Amazon. Thoughts on this product?

Lastly, I do have a hi-tech set up with an inline atomizer on the outflow, as well as a DIY PVC spraybar. So the outflow would go:

Fluval 406 > Inline CO2 Atomizer > Inline Heater > Spray Bar in tank

Sounds like a lot of back pressure there. Would love to make the inline heater work, doubly so because it would allow my CO2 more time to dissolve. But I just don't know if a single inline heater is doable due to the coldness of the room.

Thoughts?
 

nikm128

Get an aqueon 250-275 watt adjustable heater. If you want to be cautious then get the 300. That van definitely handle the cool night time temps
 

NYFishGuy

Another heater on the other side would probably work.
I'm just assuming you already have tank lids
 

Bbunkie01

Another heater on the other side would probably work.
I'm just assuming you already have tank lids

Yes, I do have glass lids, but I take them off during the daytime to minimize any light diffusion (have some sensitive high light plants).

Is an inline heater simply unfeasible for a 15f temp increase in a tank this large?
 

nikm128

I've never been able to use one for that big of an increase.
 

WTFish?

I have a 100watt in my 10 gallon for that exact reason. It’s great now, just get higher wattage, or two as suggested above.
 

Cichlidude

One 300 watt on a 75 gallon is more than enough. Why? I have the same for the past 8 years on my 75 gallon going to 62 at night also. Never failed.
 

Bbunkie01

One 300 watt on a 75 gallon is more than enough. Why? I have the same for the past 8 years on my 75 gallon going to 62 at night also. Never failed.

Hmm. I currently have a single 300w heater in-tank positioned horizontally under a spray bar. Also have two 240gph powerheads next to it to push warmed water down the tank. Never gets the temperature to the desired 77f, according to the thermometer on the opposite side of the tank. In fact, I drop as low as 75f in the middle of the night.

Maybe I have a circulation problem?

I have close to 10x turnover with the aforementioned two 240gph powerheads plus a Fluval 406. Everything is positioned to move water from right to left in the tank. Intake is on the far left, obviously.

How is your circulation set up?
 

goldface

I don't think it's a circulation problem. I would think if the water is heated to a certain temp, then the rest of the tank would be the same. I don't think there is a cooler spot and a warmer spot. I am open to be corrected, however, since I don't use heaters at all.
 

wodesorel

If the circulation isn't good you can get warm and cool spots. Positioning the heater under the outflow can help spread the heat around, as can making sure there is enough flow in the tank so there are no dead spots.

I let my bedroom get down to 60, sometimes even cooler in the winter. I had to go with 10 watts per gallon on my 20 gallon (200W total) in order to get it stable at 80 degrees.
 

Bbunkie01

If the circulation isn't good you can get warm and cool spots. Positioning the heater under the outflow can help spread the heat around, as can making sure there is enough flow in the tank so there are no dead spots.

I let my bedroom get down to 60, sometimes even cooler in the winter. I had to go with 10 watts per gallon on my 20 gallon (200W total) in order to get it stable at 80 degrees.

I really do think it’s just an honest to goodness watts to gallons discrepancy. I have the heater feeding warm water directly into a cross tank spray bar, and flanked by two 240gph powerheads. 10x turnover overall in a river circulation setup. Circulation should definitely not be an issue, though it is a long tank (48x20x18).

Going stick another 300w on the left side of the tank and call it a day. I think people really underestimate 15+ degree temperature change demands. That’s a significant difference in temperature to stabilize around the clock.
 

Rivieraneo

I recommend (2) 200WT heaters that way you have a fail safe in the event one heater fails (happened to me a few weeks ago.) I usually account for 5 watts per gallon (5 watts X 75G = 375watts) I prefer using Aqueon Pro heaters:
 

Cichlidude

Hmm. I currently have a single 300w heater in-tank positioned horizontally under a spray bar. Also have two 240gph powerheads next to it to push warmed water down the tank. Never gets the temperature to the desired 77f, according to the thermometer on the opposite side of the tank. In fact, I drop as low as 75f in the middle of the night.

Maybe I have a circulation problem?

I have close to 10x turnover with the aforementioned two 240gph powerheads plus a Fluval 406. Everything is positioned to move water from right to left in the tank. Intake is on the far left, obviously.

How is your circulation set up?

Aqua Heat titanium heater (8 years old) set up vertically right next to a Tidal 75 intake HOB. Also have a Sunsun 303B, both outputs on the right 2/3rds of the tank. Input to the 303B in on the left 1/3rd. Only have a small wave maker at the left of the tank. Removed a larger wave maker on the right after I put on the Tidal 75.

If I were to turn the heater up it would probably hit 90 degrees according to the dial. Get a hand held Infrared Thermometer to test all around. I just checked mine and the water is 77.9 degrees on the left and right sides, same as the little cheap digital thermometer and my strip on the right side.
 

Cichlidude

I recommend (2) 200WT heaters that way you have a fail safe in the event one heater fails (happened to me a few weeks ago.) I usually account for 5 watts per gallon (5 watts X 75G = 375watts) I prefer using Aqueon Pro heaters:

You do know that two 200 watt heaters only heat to the level of one 200 watt heater right? They are not additive. Only reason to add two heaters is for redundancy and temperature stability.
 

nikm128

You could position the heater near the filter intake so it pulls warmer water toward it and spreads it around once the water gets to the outtake. I also disagree with some of the above. Two heaters will be benificial depending on the placement; if you have one on opposite sides of the tank that should help with the cool spots.
 

Cichlidude

You could position the heater near the filter intake so it pulls warmer water toward it and spreads it around once the water gets to the outtake. I also disagree with some of the above. Two heaters will be benificial depending on the placement; if you have one on opposite sides of the tank that should help with the cool spots.
Yes that's why I said... Only reason to add two heaters is for redundancy and temperature stability.
 

jmaldo

Bbunkie01
As mentioned with that type of temp swing I would use 2 heaters. they will work together in maintaining the temp you desire. Best of Luck to you.
 

nikm128

Yes that's why I said... Only reason to add two heaters is for redundancy and temperature stability.
Oops, sorry. I misread that
 

NYFishGuy

You do know that two 200 watt heaters only heat to the level of one 200 watt heater right? They are not additive. Only reason to add two heaters is for redundancy and temperature stability.

I don't understand what you're saying, if both heaters are on that's 400 watts.
Level of heating is controlled by thermostat and limited by wattage.
 

Cichlidude

I don't understand what your saying, if both heaters are on that's 400 watts.
Level of heating is controlled by thermostat and limited by wattage.

OK, here we go. You have 2 heaters in parallel. (200+200)/2 = 200

All things being equal, with ambient air temperature.

If one 200 watt heater can only heat a tank to 70 degrees maximum and no more because of the ambient air temp.

Adding a 2nd 200 watt heater can only heat a tank to 70 degrees also and no more because the water is already at 70 degrees.

Think of it this way. You have a 200 watt heater running max out at 70 degrees water temp.

What if you add a 100 watt heater (which can't do 70 degrees)? It will do no good as the 200 watt heater is greater. The 100 watt heater will shut off below 70 degrees because that's all it can do.

What if you add a 150 watt heater( which still can't do 70 degrees)? It will do no good as 200 watt heater is greater. The 150 watt heater will shut off below 70 degrees because that's all it can do

What if you add a 200 watt heater? It will do no good as the 200 watt heater is the same. Both 200 watt heaters will cycle on and off trying to maintain the 70 degrees because they can't get the temperature any higher.

When I posed this question to Eheim, just to check my math, I received this from Eheim.
********
The heaters ability to heat the water will also be based on ambient room temperature. In general a heater will heat the water up 10'F above the ambient room temperature. The set temperature on any given heater will heat within +/- 1'F based on assumed near perfect accuracy, adding additional heaters will help stabilize the temperature of the water but it will not increase the overall ability to heat a given volume of water.
********
Therefore you have equilibrium (stability) in water temperature. Basic fluid dynamics haven't changed in since I was in college.
 

NYFishGuy

f one 200 watt heater can only heat a tank to 70 degrees maximum and no more because of the ambient air temp.

Adding a 2nd 200 watt heater can only heat a tank to 70 degrees also and no more because the water is already at 70 degrees.

Think of it this way. You have a 200 watt heater running max out at 70 degrees water temp.

What if you add a 100 watt heater (which can't do 70 degrees)? It will do no good as the 200 watt heater is greater. The 100 watt heater will shut off below 70 degrees because that's all it can do.


Still not following the logic. If the water temp isn't what the heaters are set at the heaters should stay on.


I've only tested similar ideas with boiling water, example 1000 watt burner couldn't maintain boil but dropping in another element of lesser wattage (or Turning on more heating element rings) will raise the temp to boil. I can't see what's different about doing the same thing with lower temps.
 

Cichlidude

Still not following the logic. If the water temp isn't what the heaters are set at the heaters should stay on.


I've only tested similar ideas with boiling water, example 1000 watt burner couldn't maintain boil but dropping in another element of lesser wattage (or Turning on more heating element rings) will raise the temp to boil. I can't see what's different about doing the same thing with lower temps.

Even more simple. If you have 2 pots boiling water at 212 degrees and you pour one pot into the other the temperature is not 424 degrees. It's still 212.
 

NYFishGuy

Even more simple. If you have 2 pots boiling water at 212 degrees and you pour one pot into the other the temperature is not 424 degrees. It's still 212.

That sounds like a horrible comparison to what I said about my experience of adding wattage through multiple heating elements to boil water.
Just have to agree to disagree until I see something scientific.
 

Cichlidude

Still not following the logic. If the water temp isn't what the heaters are set at the heaters should stay on.


I've only tested similar ideas with boiling water, example 1000 watt burner couldn't maintain boil but dropping in another element of lesser wattage (or Turning on more heating element rings) will raise the temp to boil. I can't see what's different about doing the same thing with lower temps.

In this example if you put in 20... 1000 watt burners what would the water temperature be? If this were true you just solved the energy crisis.
 

bizaliz3

Both 200 watt heaters will cycle on and off trying to maintain the 70 degrees because they can't get the temperature any higher.

I thought heaters stayed on if you had the thermostat set to a certain temp....the heater won't shut off unless that temp is reached....that was my impression.

Regardless...while I do understand your point, I do think water volume needs to be considered. A single 100W might have trouble getting the water to a certain temp simply due to the size of the tank. So a 2nd 100W heater teaming up with the first one will allow the heaters to keep up with the water volume. So in that case, a 2nd heater DOES make the water warmer. Right??? Even if it is the same wattage.

Adding a 2nd 100 watt heater can absolutely add warmth to a tank that previously only had one.

My 300w heater keeps my 75 gallon at the perfect temp. If I had a 100W instead...then the temp may not get as high as I would like because the smaller heater would struggle to keep up with the size of the tank. Two more 100 watt heaters may not exactly mean you now have 300 watts... or does it? I mean, you have 100watts in 3 different places. You may not have increased the strength, but you increased the amount of heat being given off. So additional heaters helps. It does.
 

Cichlidude

I thought heaters stayed on if you had the thermostat set to a certain temp....the heater won't shut off unless that temp is reached....that was my impression.

Regardless...while I do understand your point, I do think water volume needs to be considered. A single 100W might have trouble getting the water to a certain temp simply due to the size of the tank. So a 2nd 100W heater teaming up with the first one will allow the heaters to keep up with the water volume. So in that case, a 2nd heater DOES make the water warmer. Right??? Even if it is the same wattage.

Adding a 2nd 100 watt heater can absolutely add warmth to a tank that previously only had one.

My 300w heater keeps my 75 gallon at the perfect temp. If I had a 100W instead...then the temp may not get as high as I would like because the smaller heater would struggle to keep up with the size of the tank. Two more 100 watt heaters may not exactly mean you now have 300 watts... or does it? I mean, you have 100watts in 3 different places. You may not have increased the strength, but you increased the amount of heat being given off. So additional heaters helps. It does.

And that is called temperature stability. Remember the heater may stay on but it can not raise the temperature any higher than 70 degrees because the ambient air temperature is lower causing greater loss than can be maintained.
 

NYFishGuy

In this example if you put in 20... 1000 watt burners what would the water temperature be? If this were true you just solved the energy crisis.

Well the 1st would maintain 180 turning the second on I'm at 200, with the 3rd on I'm at 212, with the 4th+ i'm just vaporizing water faster.
 

bizaliz3

And that is called temperature stability. Remember the heater may stay on but it can not raise the temperature any higher than 70 degrees because the ambient air temperature is lower causing greater loss than can be maintained.

Sure...its keeping the temp stable. Yes. But...if the single 100W couldn't get the temp to the right spot to begin with....then the 2nd 100W heater is doing more than just keep it stable. Its keeping it a tad warmer too.
 

Cichlidude

Sure...its keeping the temp stable. Yes. But...if the single 100W couldn't get the temp to the right spot to begin with....then the 2nd 100W heater is doing more than just keep it stable. Its keeping it a tad warmer too.
Within the limit of +/- 1 degree of the heater only. Again, can't change fluid dynamics and already proven with Eheim stating the same.

And since all heaters are not the same, one could heat to 70 degrees while the identical heater could heat to 75 degrees. Thus you would see that 'both' heaters will heat to 75 degrees. Have to allow for a variance. And that's what people see.
 

wodesorel

In actual practice:

One 100 watt heater got the temperature to 75 and would not shut off.

Two 100 watt heaters got the temperature up to 86 when I was battling ich, and cycled on/off normally.



When both heaters are set to a higher temperature then what the tank is actually at, both heaters will turn on and run together until the set temperature is reached. That means the total watts are operating on the entire volume of the tank all at once. Just make sure they are on opposite ends so they both warm and cool at the same rate. Putting them close together will make them go haywire.


The same is true with the boiling water analogy. One small burner is not enough to boil water quickly, but one large burner is. Alternatively, two small burners on the same pot would work much faster than one by itself due to the increase in watts/BTUs. Comparing two separate pots would never work as that would be the same as having two separate aquariums that weren't sharing water.
 

Cichlidude

In actual practice:

One 100 watt heater got the temperature to 75 and would not shut off.

Two 100 watt heaters got the temperature up to 86 when I was battling ich, and cycled on/off normally.

Again explained by varying ambient temperature and the difference in quality control of the 100 watt heater. One can heat to 75 and the other can heat to 86. Happens all the time.
 

nikm128

I think we should be helping op pick a heater. Not arguing about our opinions on how they work....
 

Cichlidude

I think we should be helping op pick a heater. Not arguing about our opinions on how they work....
And you are right! I just don't want him to think that putting in two smaller heaters will keep his tank at the correct temperature when it gets cold at night and the temperature in the tank now drops kills his fish.

Simple, spec your tank for one heater. Adding a second will help with stability of the heat and redundancy.
 

NYFishGuy

I think we should be helping op pick a heater. Not arguing about our opinions on how they work....

OP already made decision, but it is interesting to see "quality control" factor in addition to the science of fluid dynamics.
 

Cichlidude

OP already made decision, but it is interesting to see "quality control" factor in addition to the science of fluid dynamics.
True. I have a perfect example that just happened with my new 10 gallon tank.

Ambient room temperature 68 degrees here in the TV room. Got a 50 watt heater for the 10 gallon and it would only heat to 71 degrees. Cycling on and off. Tested by turning it down and it stayed on. Kept it for 4 days running at 'full blast' and only got the tank to 71 degrees, still turning off and on. I needed 75.

Heater worked... but had an issue right because a 50 watt heater should easily heat to 75 degrees with an air temp of 68 right?

Anywho, sent it back and put in an Eheim 75 watt which will cook the fish if not turned down.
 

Bbunkie01

Thanks to everyone here.

I picked up another digital Finnex 300w, and placed it vertical alongside the Fluval 406 intake. Water almost immediately leveled off around the tank at 77f. We'll see how things go tonight when the ambient temperature of the room reaches 62f.

I don't foresee a problem, though, maybe 1-2f temp drop at most. I changed my circulation set up, as well. Put one of the 240gph powerheads on the top left of the tank, pointing down and diagonal into the water column. This should create the classic whirlpool circulation around the tank.

Lastly, and importantly, I do take off my glass lids during the day during lights on. I have a rotala macrandra in particular that needs as much uninterrupted PAR as I can give it. I put the lids back on at night.

Thanks again for all the replies.
 

Rivieraneo

You do know that two 200 watt heaters only heat to the level of one 200 watt heater right? They are not additive. Only reason to add two heaters is for redundancy and temperature stability.

Correct, hence my comment. One on each side of that tank can maintain set temp on their own side and in the event one fails, you are left with one working heater to at least help maintain.

You can go with one large heater, but if it fails in the cold environment the OP has described, you would risk complication due to temperature
 

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