Heater size for 65 gallon aquarium

[Gregs_Gal]

Hi, I currently have a 200w heater in my 20 gallon that I love (because its adjustable from outside the water). My nephew just gave me their 65 gallon aquarium. I would like to keep that heater. Would it be big enough for a 65 gallon or do I need to get a 300w? The dimensions of the new tank are: 48×12.5×24.75. I am keeping guppies and I keep their temp between 76°-78°. In the summer I will go up to 80° because that's what my tap water runs. My house runs 80° during the day and 74° at night. In the winter we keep it around 70° during the day and 65° at night. Thank you for your help! 

Edited July 29, 2022 by Gregs_Gal

[Flumpweesel]

How many degree's do you need to lift the temp ? 

[Gregs_Gal]

On 7/29/2022 at 7:05 AM, Flumpweesel said:

How many degree's do you need to lift the temp ? 

I have guppies so I usually keep it around 76°-78°. In the summer I will go up to 80° because that's what my tap water runs. My house runs 80° during the day and 74° at night. In the winter we keep it around 70° during the day and 65° at night. Thank you for your help! 

Edited July 29, 2022 by Gregs_Gal

[Flumpweesel]

Well it sounds like you will barely need a heater in summer so it will be fine, it might struggle in winter but that depends on so many things I would say try it and if its not keeping up you can add a secondary 100w later. 

I think my old heater in a similar sized tank was 200w I replaced it ( after it died 8 10 years later) with a 300w because the 300w in the shop had better shielding and wasn't much more expensive.  As long as it isn't constantly turning itself on then it's coping. 

Heaters always seem like they should be a formula to say what you need but with so many variables it is hard it work out what is best. 

 

[Gregs_Gal]

On 7/29/2022 at 7:40 AM, Flumpweesel said:

Well it sounds like you will barely need a heater in summer so it will be fine, it might struggle in winter but that depends on so many things I would say try it and if its not keeping up you can add a secondary 100w later. 

I think my old heater in a similar sized tank was 200w I replaced it ( after it died 8 10 years later) with a 300w because the 300w in the shop had better shielding and wasn't much more expensive.  As long as it isn't constantly turning itself on then it's coping. 

Heaters always seem like they should be a formula to say what you need but with so many variables it is hard it work out what is best. 

 

Thank you! I appreciate the help! 

[Cheryl P.]

I have a 200w in my 65 gallon discus tank and it's been working great.  I keep the tank in the mid 80s.  A glass lid really helps out with keeping the heat in.

[Gregs_Gal]

On 7/29/2022 at 9:21 AM, Cheryl P. said:

I have a 200w in my 65 gallon discus tank and it's been working great.  I keep the tank in the mid 80s.  A glass lid really helps out with keeping the heat 

Thanks!  Glad to know it would work! 

[quikv6]

So in my opinion, 200W will be PLENTY given the average room temp. (I would personally do it with 2-100W heaters, though....for safety, in case one fails).

I just set up a 125 6 foot tank recently. My room temp is 69-70. I threw a single 100W heater in it. It took a while to heat it to 78-79, but it is holding like a rock.  I never thought a 100W would be sufficient for a 125, but it is doing great. Given you have half the amount of water and double the wattage, I think you will be just fine. In fact, you could probably go less.

[Gregs_Gal]

On 7/29/2022 at 9:40 AM, quikv6 said:

So in my opinion, 200W will be PLENTY given the average room temp. (I would personally do it with 2-100W heaters, though....for safety, in case one fails).

I just set up a 125 6 foot tank recently. My room temp is 69-70. I threw a single 100W heater in it. It took a while to heat it to 78-79, but it is holding like a rock.  I never thought a 100W would be sufficient for a 125, but it is doing great. Given you have half the amount of water and double the wattage, I think you will be just fine. In fact, you could probably go less.

Thanks! That definitely puts my mind to rest. 

[ccc24]

I honestly wouldn’t heat it in the summer. I have the same tap issue (water comes out at 80) and with partial water changes, it doesn’t shift the temp much in my large tanks. It matters in my 6g but not in the 55g. I do keep fish that aren’t known for being sensitive (things like guppies, acara, mollies, rainbows not discus or rams). 
In the winter I’d just run two 100 watts. Less likely to fail and you’ve got a back up (and much easier to hide in the decor). I personally keep two ACO 100 watts in my 55g (one on each side) but it’s overkill in the summer. It’s more as a back up (one gets shut off most of the time) then anything. 1 was able to the job, I just like building redundancy into my systems.