# heaters - cycle on/off every 2 hours?



## Martindale (Sep 2, 2009)

I have 20 2-3" Moba in a 180 gallon 6x2x2 w/2 300 watt tank heaters. I am using only 600 watts because Im concerned that equipment failure/malfunction could occur. IMO with only 600 watts (about 300 watts shy), in the event of a mis-hap, being short on the wattage would help. The tank is in my garage that has been converted into a 400 sq. foot 5th room(my fish room). Its Radiant Barrier insulated, carpeted, air conditioned and has a 1500 watt convection heat supplemental heater on a timer that turns on at 6pm and shuts off at 10am. The room stays between 68 - 74 degrees and the non heated water temperature averages between 70 - 72 degrees. The Moba 180 w/600 watts in heaters has been staying at 78 degrees.
I have also been told to take a different approach: use the proper wattage (900 watts) that way the heaters will cycle off and wont run as much. In this event the way to safe-guard against heater mis-haps causing dangerously high temps is to run the heaters on a timer...2 hours on and 2 hours off...2 on 2 off...and so on...
I would really appreciate some input on this. Let me know what ya think. Thanks! opcorn:


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## prov356 (Sep 20, 2006)

Put both of your 300 watt heaters on a single, high quality controller. Check them out at Jehmco.

How did you come by the value of 900w as the 'proper wattage'? A single 400 watt for a 68 degree room is probably all you need.


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## Martindale (Sep 2, 2009)

I was told to run 5 watts per 1 gallon of water. Is this correct?


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## aspen (Jun 15, 2004)

if the wattages of the heaters you are using, are maintaining the temps you want, in YOUR conditions, then they are right.

the perfect size of heaters would never shut off. that little spark you see when a switch opens is actually burning the contact area. although it is rated for that, staying on is actually better.

rick


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## noddy (Nov 20, 2006)

900w in a 180? Not something I would do. I run two, 250w heaters in a 210, and I run one, 250w in each of my 120's. In my case, 2w per gal. is plenty.


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## Cento (Mar 30, 2005)

noddy said:


> In my case, 2w per gal. is plenty.


 In the vast majority of cases, 2w per gal is plenty. 5w per gal is far to high, especially with the ambient temperatures you say the room is at. If you ask some of the members who've been at this for while, 2w-3w per gal is the rule-of-thumb for many reasons (economy, designed working range of heaters, less chance of heater failures ending in catastrophe, etc).

Now, there are many arguments as to how the wattage should be divided (ex: 2 x 150w vs 1 x 300w, etc). But usually, that comes down to your own line of reasoning. There are also ways to make heaters more efficient (placement, water flow, in-line heating, etc).

I think you should be fine. Good luck with your fishkeeping!


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## fox (Jun 11, 2009)

I have two 300W hydors inna 225G system here in the NE, USA. We keep the room on the cool side at about 65Ã‚Â° F during our colder winters. I originally set them up so both would go on and maintain 80Ã‚Â°F and confirmed they would both cycle on and off.

We have since found that after a few days only one will sense the demand to operate and stays on and is able to maintain tank temp. Even on our colder nights here when the temps drop into the single digits the other hydor rarely operates. If I raise the temp on that one the other does not meet the demand to operate ... the baseboard heat runs behind the tank and my guess it is contributing BTU's.


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## prov356 (Sep 20, 2006)

Martindale said:


> I was told to run 5 watts per 1 gallon of water. Is this correct?


There is actually a formula for figuring out wattage. Here's a calculator that I've found to be fairly accurate. Room temp, thickness of glass/acrylic all come into play. The old 5 watts per gallon rule is oversimplistic, but works for most, so that's what's often recommended. Risk comes in when you have more wattage than needed. If it sticks on, it could overheat and kill your fish. I came up with the 400w that I recommended to you based on the linked calculator. Plug in your tank dims, thickness of glass, coolest temp you expect in the room, etc.

There's some good info here on Jehmco's site regarding why two heaters may work erratically if not on a central controller. Scroll down to the bottom of the page.

HTH


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## Martindale (Sep 2, 2009)

Man, keep the info coming. This is great. Im really glad I asked.


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## mg426 (Nov 24, 2009)

I use a Ranco temp.controller to run a pair of 250s in my 125. I have no trouble maintaining 78 degrees. The temp is rock steady.


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## Cento (Mar 30, 2005)

+1 on the temperature controller.

It's a good buy as far as fishkeeping goes. People spend upwards of $150-$300 for their filtration systems ($400-$600 if you're talking the Fluval G series  ), but some only spend $15-$40 on there heating system. Something that can potentially kill your fish if it's not working properly (too hot OR too cold).

Temperature controllers can arguably extend the life of your heaters. Also, IMO, they are more accurate in regulating temperatures in your tank, since most of the temperature probes can be placed far from your heating sources, therefore regulating the temps that represent the majority of water volume, as opposed to hot spots, if that makes sense.

I got a cheap one from Hydor for $50 (mind you, Hydor is a very good brand). There are some out there with a few more desirable options for about 50 bucks more. Either way, its still one of the cheaper components of your aquarium setup.


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## SupeDM (Jan 26, 2009)

If you have the tank in a specail fish room with supplemental heat it would be alot easier to heat the room and not the tanks. You wouldn't have to horry about cooking the fish with heater malfunction. Wouldnt need heaters at all.


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## JHenriksenCVM (Jan 21, 2010)

Get a 400w Rena Smartheater, extremely eficiatant, safe, and strong. I bought one and I'll never buy anything else. They also don;t look as bad in the tank as others.

P.S. you don't want your heater to run 24/7 and never shut off, that means its working too hard and is too small for your tank.


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## highflyingk9 (Nov 2, 2009)

After reading this string, i had come to the conclusion that i was over powered! My set up is a 72g at 79C, with a room temp of 60 (basement), heated by a rena smartheater of 300W. It seemed to work perfect, but i was concerned about its eventual failure and frying my fish. I plugged my specs into the equation provided by the link a few posts above and got a number just shy of 200W needed. Off i went to the lfs and purchased a rena 200W smarty. Well that was last night, and my tank still hasn't reached 79. The heater has been on constantly, and the temp is hovering just below 78. I suppose an acceptable number, but it appears that the heater is maxed out, something that my fish wont appreciate, but my hydro company will....
back to the 300Wer


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## Martindale (Sep 2, 2009)

Here are some things that came to mind when I read the last post. First if you dont already have one you can get a digital thermometer at you LFS for around $10 and they work good for situations like this. Lets say the 200 is the desired heater. Maybe if the 300 is more effecient at raising the temp then try setting up both heaters, and running _*only*_ the 300 watt heater and stabilizing the temp. Now turn the 200 on at a low temp. From there do a gradual incline/decline on both heaters. Pay very close attention, use your best judgement and when you are confortable turn off the 300. Maybe the 200 will hold the temp just fine once the temp has stabilized. Now please remember I just got home from work and started typing soooo if anyone thinks that something I have said is a "NEVER DO" kinda thing then please jump in and say something. I have never used my incline/decline idea so it is "unproven". This all came to mind when I noticed you mentioned that the temp had not got back to 79 and the 200 had been running constantly. This led me to belive that there was a drop in the temp in your tank. Did the temp drop? If "yes" then do you know why?


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## prov356 (Sep 20, 2006)

The calculator works fine, and did so for you, but you have to understand what it's giving you. It gave you a wattage that would be able to just get the temp to 79 and no more. And that's what it did. You always have to give a +/- one degree variance allowance with aquarium grade thermometers, etc.

The way to use the calculator to size a heater is to not actually plug in the desired running temp, but the desired *MAX *temp. Not knowing the dims, etc of your tank, I can't do that, but put in all the dims, and this time put in a desired temp of 85 or whatever you want the max to be. Go with that size heater because that's the maximum temp that it can ever raise your tank.

Another way to use the calculator is to keep trying different temps until you get one that gives you 300W as the required heater. Then you'll know the capability of your 300w heater. Hopefully it won't be into the 90's. If it is, then the heater is too large.

One other thought. If in doubt, go with the lesser size. Cool temps in the mid 70's don't kill, but temps in the 90's do. Many seem to go just the opposite and when in doubt go with 'more power'.


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## highflyingk9 (Nov 2, 2009)

thanks for the advice guys (or girls)...

Martindale- my tank temp had dropped because i neglected to mention the part of the story where i bought a fluval heater that wasnt functional (my tank was w/o heat for about 2 hours while i sorted things out). it dropped 3 degrees.

prov356- sorry if you thought i was questioning the calc. referal. i was just informing that for my situtation the numbers didn't quite match up for what i needed. however, plugging in max temps gives very valuable information...thanks.
I have found that for my specs at 60F ambient, a 300W heater will never raise the tank temp above 87. nice. unfortunately when summer rolls around and the bsmt gets above 65, my 300W could be lethal...
Ideally i should be controlling my bsmt temp to be about 65F, and using the aforementioned 200w heater :thumb:


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## prov356 (Sep 20, 2006)

> I have found that for my specs at 60F ambient, a 300W heater will never raise the tank temp above 87. nice. unfortunately when summer rolls around and the bsmt gets above 65, my 300W could be lethal...
> Ideally i should be controlling my bsmt temp to be about 65F, and using the aforementioned 200w heater


You're exactly right and that's the right way to deal with it. Consider conditions for every season. If the room temp is going to vary considerably between seasons, consider seasonal heaters, and swap them out as needed. Go with a lesser wattage during the hot summer months.


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## highflyingk9 (Nov 2, 2009)

seasonal heaters, yes  . much simpler than trying to regulate room temp. thanks again.


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## punman (Oct 24, 2003)

When I had a 180 gallon tank I used a 250 W heater = 1.4 W/gal. It was on 31.4% of the time (I monitored it over several days at random times). Heater set for 77.5 F and house temperature averaging 71 F. 
My smaller tanks that were 1.5-2 watts per gallon were actually having the heaters on more often as a smaller body of water cools quicker.


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