# Proper wattage for heaters



## TKC747 (Dec 5, 2008)

I lost my three melanchromis johanni - exellent specimen to a heater which fused and heated the water up to 90 degrees for more than 6 hours. What is good for a 55 gallon malawi tank so as to not repeat this mistake.

Thanks in advance

TKC747


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## TKC747 (Dec 5, 2008)

Sorry  I found just the thread I needed...don't waste your typing sorry once again

TKC747


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## Vincent (May 7, 2004)

Maybe a year or more ago someone posted a formula that took into account the ambient temperature, glass thickness, surface area, and maybe other factors. You can probably find it by searching. It gave me a value of 112W to keep a 55G tank at 80 in a 65 room. So I think a 150W heater would be fine.


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## b_tenant (Apr 9, 2007)

I have heard some people advise getting the largest heater you can fit comfortably. A large heater will cycle less and last longer is the theory.


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## b_tenant (Apr 9, 2007)

Curse this crummy comptuer. Sorry for the double post.


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## prov356 (Sep 20, 2006)

> A large heater will cycle less and last longer is the theory.


The 'cycle' of the heater depends on how fast two things happen, the heating of the water and the 
cooling of the water. The cooling of the water will take the same amount of time regardless of the 
size of heater. On the other hand, a larger heater will take less time to heat up to the max 
point where it shuts off. Larger heaters will cycle on and off more than lesser wattage heaters.

All heaters have a max and min point that's about +/- 1 degree. If you set at 78F, for instance, 
it'll heat up to 78.5 (max point), turn off, water will cool to 77.5F (min point) and then the heater 
will turn back on. If a large heater takes half the time as a lesser one to heat to max, then it'll 
have a 25% faster cycle time, so more cycles in a day.

Whether or not cycling more causes them to not last as long, that I don't know.

Here's a site with a wattage calculator. Most use way too high of a heater thinking more is better, 
but it can also cook your fish faster. I use less than 2 watts per gallon on a 180 gallon tank.

HTH


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## alicem (Jul 26, 2007)

> I use less than 2 watts per gallon on a 180 gallon tank.


I'm curious, do you use one heater at each end for more even heat and these are rated 150W each?

Tim, you've opened a can of worms. 

So I'm wondering... which is more cost effective or how could you calculate it? 
A smaller heater that stays on longer to get the temp up and runs less often or 
a large heater that runs hotter for a shorter time, but more often?

Not a math whiz, but can fake it,
Alicem


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## prov356 (Sep 20, 2006)

alicem said:


> > I use less than 2 watts per gallon on a 180 gallon tank.
> 
> 
> I'm curious, do you use one heater at each end for more even heat and these are rated 150W each?
> ...


I use a single 300 watt in my sump. If you use two heaters without a controller, it can be 
difficult to get them to work together. One may never even come on if one is enough to heat 
the tank. Consider the min/max points. It'd be hard to get them set exactly the same so you 
might have one with a min/max of 77.5-78.5 and the other with a min/max of 77.7-78.7. If the 
second heater kicks on at 77.7 and the water never drops down to the first heater's min of 
77.5, it won't kick on. Temps could fluctuate enough that it may drop at the end of the tank
where that heater is placed, but it'd be sporadic. I only mention all of this because many have 
recommended using two for redundancy.

I did a log one time and was surprised by the results. I watched the heater to see at what 
temp it kicked on and off. I was using a pretty good digital thermometer, so I could see tenths 
of a degree. It literally took hours for the 'cycle' to complete. Meaning over an hour to raise 
it high enough to kick off and then over an hour to drop low enough to kick back on. I don't 
remember the times exactly, but too long to sit and watch like I expected. The size tank will 
have something to do with this. It's also acrylic which holds temps better than glass. The room 
and tank temp differential comes into play too. The room is 72, and the tank is 78, so the air 
temp, while working to lower the tank temp, wasn't real aggressive about it.

As for cost, it's all about kilowatt hours. If you use a 200 watt heater and it reaches it's max in
half the time as a 100 watt, then it's a wash. If that same 100 watt heater struggles to heat 
the tank, it might run for 3-4 times longer than the 200, or it might run continuously. I think 
the only time you start overspending for electricity is if you have a seriously undersized heater 
that can't keep up, so it's almost always on trying to raise the temp that one degree to it's max 
point. I think once you start comparing heaters that are both capable of heating the tank, it'll 
wash. There is a neat little device that you can get that'll tell you exactly what it costs to run 
any elextrical appliance. It's called Kill-A-Watt. I have one and have used it to determine exactly 
what you're asking about. I have some 100 watt heaters on some rearing tubs in the 
basement where it's cooler and they struggle to keep up. I found that they run for over 20 
hours per day.  I need to replace those things, but haven't done it yet. The sad part is that 
when I purchased the heaters, I didn't want to go higher than 100 because of the cost of 
electricity. I naively figured that a 150 or 200 watt heater was going to cost a fortune to run, 
since I needed one for each of 4 tubs. And those are 25 gallon tubs, so it's 4 watts per gallon. 
But they're sitting just off the cold concrete floor where ambient temp is 60 some degrees. I 
plugged this data into that calculator and sure enough, it even said my heaters were shy of 
what's needed. Play around with that, plugging different room temps and tank sizes and glass 
thicknesses, and it's really pretty interesting to see the results. I've found that calculator to be 
pretty accurate.

Always a pleasure alicem.


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## moneygetter1 (Jan 8, 2006)

Good post _*prov 356*_. I posted the following previously. (different forum) A little different angle, but still something to ponder.



> _don't see any wisdom in wasting money. The bottom line is using two heaters is completely unnecessary unless 1 heater isn't enough to keep the tank heated or you don't have central heat. If the heater fails the tank water is only going to drop to room temperature which is not likely to have any ill effects on the vast majority of tropical freshwater fish until it can be replaced. So why waste the money? _
> 
> From a previous post for 'BIG' tanks -
> The reason for splitting the difference of the wattage necessary to efficiently heat 'X' amount of water is to safeguard against the possible failure of the heater in the 'on' position. Failure of one of two or three in the 'off' position, although serious, is usually not as critical because room temp. will usually assist in keeping the tank warm. (most fish can survive cooler temps. longer than high temps.) In either event, it will give the aquarist more time to recognize that there is a problem before it becomes catastrophic. Temp. controllers can also aid in keeping a failed heater in a multi-heater setup from destroying your fish. Most calculate using approx. 3 to 5wpg. Also multi-heater setups in large long or deep tanks usually distribute the heat better preventing excessively cold or hot spots. I know some who have been successful w/ a single 800w titanium heater but I would rather have 2 - 350w or 3 - 250w running thru a controller for safety & redundancy. Pre-heating the water in a sump before going to the main is another way to achieve even heat distribution. I've run thru a number of different heaters but right now I'm satisfied w/ 2 - 250w heaters running thru a D58 controller from Won Bros. JMPO, "T


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## alicem (Jul 26, 2007)

Yes, of course, room temp. _would _have a lot to do with heater "run time."
I plugged the numbers for my 90G sitting in my livingroom, into the "wattage calculator" in the earlier post and it indicated I need a 28W heater.
:lol: We keep our house right around 78 degrees, summer and winter.

My daughter had to run a mathmatical equasion for estimating eletrical cost for appliances in our home when she was in school.
Sad to say, my beloved coffee pot was the worst offender. :roll:

And, Tim, as soon as I posted, I remembered you have a sump on your 180G. 

At the risk of this having already been hashed over in other posts and hoping this is relevent to the OP's question:

Where would the most beneficial/economical placement for a heater be in the tank? 
(beneficial to the fish and bacteria) (economical use/distribution of heat)

Under the return? at the intake? the side nearest an exterior wall?

Are the benef. bacterial in the filter as susceptible to temp. changes as our fish are?
I wonder, what temp. extremes bacteria can survive at? Like when the temp. rose in TKC747's tank or when someone moves in the winter.

Alicem


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## prov356 (Sep 20, 2006)

> We keep our house right around 78 degrees, summer and winter.


You don' t even need a heater, it would seem. What temp do you keep the tank water? 78 in the winter 
too? I'd be opening windows. :lol:



> Where would the most beneficial/economical placement for a heater be in the tank?
> (beneficial to the fish and bacteria) (economical use/distribution of heat)


I usually go for near a filter intake. The water's quite warm as it comes off the heater, but would cool 
down quite a bit by the time it got to filter bacteria. I wouldn't think it would have any effect either good or 
bad.



> I wonder, what temp. extremes bacteria can survive at? Like when the temp. rose in TKC747's tank or when someone moves in the winter.


I don't think anyone really knows that for sure. I"ve never heard of having to re-cycle when these 
heater problems happen, so it seems they can be ok at temps outside of what's ok for fish. Don't 
know though.


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## alicem (Jul 26, 2007)

Interesting, thanks!


> > We keep our house right around 78 degrees, summer and winter.
> 
> 
> You don' t even need a heater, it would seem. What temp do you keep the tank water? 78 in the winter
> too? I'd be opening windows.


The tanks are around 78-80.
Wood heat (propane furnace backup when we're not home) and yes, when it has gotten away from us, we've had to open the door. 
Alicem


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## NORMAND (Oct 27, 2008)

very very good site thanks guys. was just wonderin about all this to


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## TKC747 (Dec 5, 2008)

Thank you everybody, you all gave me good points to think about, but here's the bottom line, if you're away for a long time, you'd better have a quality heater. This is one expensive hobby :lol: but worth every dime  :thumb: Thanks again


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## rancherlee (Sep 15, 2008)

2 heaters is the way to go. 
One 200w is more than enough for a 55 gallon. Mine heats my 55 gallon to 80*f in a 58* basement with some headroom left (a.k.a. the heater isn't on all the time) I just migrated to the new 125 gallon tank and One 200w heater gets it to ~70*f in the same basement, and it holds 80*f just fine with 2 200w heaters. This is setup so if one heater dies or "malfunctions" the tank won't over heat OR get to cold.

With a 55g I would run 2 100w heaters unless your house is 70*f+

The formula I seem to remember is 1 watt will heat 1 gallon about 6*f though it varies on if you have an open top, closed top, sump, ect.


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