Heater Discussion: Difference Between "Low to High" vs. "Exact Degree" Heaters

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daveman12345

Feeder Fish
MFK Member
Jul 17, 2008
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Hi guys,

In the last two years I have purchased a number of filters since my Oscars have broken them. There are two kinds, and I'm trying to figure out what the difference is.

1. Low to High - These filters have a "low to high" setting so that depending on the temperature of the room, it fluctuates. For example, if it's 99degree outside, the tank will go to about 95 degrees and if it's 60 degrees outside, the filter will go to 83ish.

2. Exact Degree - These filters tell you exactly what degree you set it to, for example 80degree setting on the filter and it only kicks in if the temperature falls below this.

From my understanding, it seems like the "Exact Degree" filter works best. Is this true? Do they automatically have temperature settings in them so that they only turn on when they have to?

I'm a little traumatized from one of my heaters overheating because I had an electronic 1000 watt heater that took my tank to 99 degrees and killed two very valuable fish. Now, instead of an electronic heater with an LCD display of the temperature, I'm looking for something that will keep the temperature constant with *little* fluctuation, and with not enough power to take the temperatures beyond a certain amount of degrees (for example, 90 degrees).
 
What you are describing is called the differential. The temperature you set on the thermostat actually determines when the heater turns off. A thermostat set to 80 with a differential of 4 degrees will turn on at 76F and off at 80F. Thermostats with a low differential will cycle devices on and off very frequently causing excessive wear.

You'll have to look at the manufacturer specs to determine the differential, it probably will not be on the retail packaging. Honestly, I don't think your tragedy was caused by differential but a defective heater.
 
Not sure what you're talking about when you say "low to high". I've never heard of a heater that varies with room temperature. Typically, you set the thermostat on the heater to the ideal temperature, and it will fluctuate within a band of a few degrees. They have to have a band, because if the heater was designed to turn on precisely when the temp dropped below the setpoint, it would cycle on and off too much, resulting in premature failure. Different heater manufacturers have different bands.

I think the best solution for you would be the Hydor ETH in-line heater. This allows you to locate the heater outside the tank, eliminating the possibility of your fish breaking the heater. Additionally, it allows for more efficient heat transfer, since the water is constantly flowing past the heating element instead of just sitting in the tank. This allows you to use a heater of a lower wattage than you would need for a typical submersible heater, so this also addresses your overheating concerns. You don't say what size tank you have, but they make a 200W and a 300W. I use the 300W on my 75g and it keeps the temperature dead-steady at 80 degrees.
 
It is not wise to blindly trust the *F setting on any heater, a thermometer is a must...


Using to strong of a heater causes the heater to stay on for short periods then turn off for short periods... This causes the on/off controler wear out much much sooner thus causing the tank to overheat...


I use 2W per gallon on my tanks and they work fine at keeping the tank at a steady 80*F even in the winter when the house dropsdown to 65*F.

I used trhee 300W heaters to keep a 300 Gal Rubbermaid at 80*F even in the winter months when the overnight temperature dropped to 65*F, despite the 23.75 square feet of uncovered surface...


Using to large of a heater is a dangerous mistake that usually results in cooking your fish...
 
bob965;3621204; said:
Not sure what you're talking about when you say "low to high". I've never heard of a heater that varies with room temperature. Typically, you set the thermostat on the heater to the ideal temperature, and it will fluctuate within a band of a few degrees. They have to have a band, because if the heater was designed to turn on precisely when the temp dropped below the setpoint, it would cycle on and off too much, resulting in premature failure. Different heater manufacturers have different bands.

I think the best solution for you would be the Hydor ETH in-line heater. This allows you to locate the heater outside the tank, eliminating the possibility of your fish breaking the heater. Additionally, it allows for more efficient heat transfer, since the water is constantly flowing past the heating element instead of just sitting in the tank. This allows you to use a heater of a lower wattage than you would need for a typical submersible heater, so this also addresses your overheating concerns. You don't say what size tank you have, but they make a 200W and a 300W. I use the 300W on my 75g and it keeps the temperature dead-steady at 80 degrees.
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Hi, thank you all for the replies. I think the external canister heater sounds great, and it prevents my fish from breaking them. To note, yes I do have a 120gallon tank, but I only fill it about 3/4 so that my Silver Arowana's don't jump out.

I looked up Hydor ETH in-line heater and found a 200watt for $40. Does anyone have better recommendations? If not, I think this will be a good investment to get.

One person asked what I meant by the "low to high" setting. This is found in regular heaters where it doesn't ask you for the exact temperature you'd like, but rather whether or not to set the heater to "Low" or to "High" with a range inbetween it. This is confusing because you kind of have to guess how hot your tank is going to be.

So, please let me know if you have a recommended heater. Right now the external heater sounds perfect.
 
Aquarium heaters can be quite temperamental and frustrating. I experienced very unreliable performance with the Hydor Theo and have read several posts discussing accuracy issues with the ETH. Titanium heaters have a lifespan that can be measured with an egg timer. Of all the heaters I have personally used, I regard the Marineland Stealth as the most reliable. It also has a black plastic covering which protects it against breakage. I can recommend it without hesitation.
 
I had a marineland stealth fail on me after 4-5 months of use. Just stopped heating. Luckily I caught it before my fish froze to death, but the lack of on/off indicators makes it very hard to tell if the heater is working properly. I guess this is better than cooking your fish with a heater though. At any rate, I've had cheap brand heaters (top fin?) for years that have not failed on me, so I'm thinking heater brands don't matter too much, just hope you get a good one and not a lemon.
 
davcheng;3631076; said:
I had a marineland stealth fail on me after 4-5 months of use. Just stopped heating. Luckily I caught it before my fish froze to death, but the lack of on/off indicators makes it very hard to tell if the heater is working properly. I guess this is better than cooking your fish with a heater though. At any rate, I've had cheap brand heaters (top fin?) for years that have not failed on me, so I'm thinking heater brands don't matter too much, just hope you get a good one and not a lemon.
Click to expand...


Stealth heaters have a lifetime warrantee... and Marineland has a solid reputation at honoring that warrantee...
 
If you have multiple silver arowanas in a partially filled 120 gallon tank I think that finding a heater is not your only problem.
 
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