Heaters- how to size a heater for your tank

[Jan Cavalieri]

I currently have a 90 gallon tank cycling quite slowly. I set the temperature on 70 F and then later read that it's better to turn up the temperature when your cycling (this is a fishless cycling and it's the new occupants that prefer 70-78 degrees. It took days to get to 70 degrees (which is what my house thermostat is set to also) but I finally got it up to 70 and then turned it up to mid-eightys and after 3 days it's only gone up to 71 degrees. The tank is so large it has some serious cold spots- I sure wouldn't want to live in there and it's way colder than these fish are use to (75-78).

I run into this time and time again, whether it's a 5 gallon betta tank or a 50 or 90 gallon tank. I pick the appropriate size heater and all the larger tanks have powerful circulation and I can rarely get the temperature up to where I need it. Do you all just use multiple heaters? This heater is placed in the center of the back panel - it's still receiving some strong circulation from the pump (it has a cannister filter). I'm just about getting ready to buy an 800 watt heater to add to the 300 w (the company I like doesn't make 500 watt heaters). I like them because they are super easy to set up and display the current temperature as well as the temperature you have it set too. If this was the ONLY heater that failed to heat properly I'd buy something else but I have yet to find a heater that keeps the temperature that it is set at. The cheap filters just run it up to 78 degrees and there is no way to adjust it. '

Any recomendations?

 

[PheonixKingZ]

I currently have a 90 gallon tank cycling quite slowly. I set the temperature on 70 F and then later read that it's better to turn up the temperature when your cycling (this is a fishless cycling and it's the new occupants that prefer 70-78 degrees. It took days to get to 70 degrees (which is what my house thermostat is set to also) but I finally got it up to 70 and then turned it up to mid-eightys and after 3 days it's only gone up to 71 degrees. The tank is so large it has some serious cold spots- I sure wouldn't want to live in there and it's way colder than these fish are use to (75-78).

I run into this time and time again, whether it's a 5 gallon betta tank or a 50 or 90 gallon tank. I pick the appropriate size heater and all the larger tanks have powerful circulation and I can rarely get the temperature up to where I need it. Do you all just use multiple heaters? This heater is placed in the center of the back panel - it's still receiving some strong circulation from the pump (it has a cannister filter). I'm just about getting ready to buy an 800 watt heater to add to the 300 w (the company I like doesn't make 500 watt heaters). I like them because they are super easy to set up and display the current temperature as well as the temperature you have it set too. If this was the ONLY heater that failed to heat properly I'd buy something else but I have yet to find a heater that keeps the temperature that it is set at. The cheap filters just run it up to 78 degrees and there is no way to adjust it. '

Any recomendations?

You would need a 270W-280W at minimum for a 90g tank, or two 150W.

Maybe the brand of heater isn’t that good? What brand are you using?

 

[Bruce Leyland-Jones]

Most of the quality heaters I've seen state the tank size they're designed for.
Be sure to get one that you can adjust the temp. Sounds obvious, but the 'value' ones often don't.

 

[Slaphppy7]

How to Size a Heater for Your Aquarium

Learn how to calculate the right wattage for single or multiple aquarium heaters, based on the room temperature and desired tank water temperature.

www.thesprucepets.com

 

[AbbeysDad]

It's a good question. An under sized heater has to work much harder (if not stay on all the time) to achieve and maintain a set temperature. On the other hand, a wattage higher than needed, the heater will draw more power, heat faster, but overall will be on less. Where possible, I like the idea of two lower wattage heaters instead of just one so the suggestion that was mentioned by @PheonixKingZ for two 150w heaters is a good one. It may or may not help much if a heater sticks on, but if one quits working, you'll have more time to discover and replace...which reminds me that a daily visual check of the temperature is very important, especially if the room gets cold (thinking winter here).
Now if money is not too tight, heaters with internal thermostats are known to fail. I have a couple of tanks with titanium heaters hooked to an external controller and these seem to be nearly bullet proof.
And this all takes us to Freshwater Aquarium Heater - Is One Really Needed? as we've all been conditioned to think we really need a heater for tropical fish to keep the temperature 76° - 78°F. However, depending on the fish we keep, typical room temperature of 72°F~ may be just fine. Admittedly higher temperatures increase metabolic rates and fish are often more active. But nature often doles out temperature swings and many fish live in cooler waters than we might think. Now I'm not suggesting that anyone should not use a heater, merely pointing out that in many cases they're far less necessary than we might think.

 

[Jan Cavalieri]

Ok thanks for the responses but I don't think anybody totally gets it and plus I worded mu question badly. I buy fairly expensive highly rated heaters off of Amazon. This brand is an AQQ nicely constructed in China for a reasonable price of $45 USD. (nearly all the heaters are from China these days). I've had fish tanks for a little over 4 yrs and I have NEVER had a heater that heated water as high as it said it would based on the size of the tank. Every one I have tried I have found to be undersized.'

I'm currently using a 300 watt heater for a 90 gallon tank - supposedly it's correctly sized but I can only get it to heat the water 1 degree over room temperature (71 degrees). Right now I would like it to hit about 83 degrees while I'm doing a fishless cycle (the higher the heat, the faster the tank will cycle and then turn it down to 78-82 for the Dojo that will eventually move into the tank. Amazingly the tank is cycling quite nicely and I think it will be done very soon (I actually got a "clear") reading on ammonia today which I've never seen before. Of course Nitrites and Nitrates are very high. But I digress

My point was that I have NEVER purchased a heater that actually met the spec's they listed on their box, not ever. They'll say 50 watts for a 5 gallon tank, and you'll find that even 100 watts isn't even sufficient to heat a 5 gallon tank when the air conditioning is on. I always use a 150. In this case I used a 300 for a 90 gallon tank 1. to test it and 2. because I was out of 500's (I keep several sizes in stock since it's been my experience that heaters break really easily. I didn't realize that the warmer the water the faster the cycling will go. So turns out the 300 watt only was able to raise the temperature up 1 degree (my thermostat is set at 70 degrees) so this 300 watt heater is only able to raise 90 gallons by 1 degree F. And I'm getting frustrated that heaters advertise that they heat a certain size tank but mine never do. I wondered if anybody besides me has ever had the same problem. There is also the theoretical issue of whether 1 large heater turning on and off all day wears it out - but if you get several smaller heater they all together will heat the way you want it and none of them with have to turn itself off and on as frequently as it would if it were the only heater in the tank. Just a theory but it does sort of explain why heater break so often,

I was thinking about getting a 500watt heater in this same brand but they don't make that size. All of the size are the easiest, best designed heater I've ever used (with the small problem that the 300 watt DOESN'T WORK LOL. So instead I'll try their 800 watt heater along with the existing 300 watt heater. If that doesn't work I'll think sad thoughts about these nicely designed heaters but get a refund on both sizes if I'm not over the 30 days. Even though the USP store is right down the street it's still a drag to return things (byw - I have a 150 of this same brand working great in at 5 gallon betta tank.

What have other people experiences been when heating 90 gallon on up size aquariums - what do you buy for say, a 250 gallon tank?

Thanks for your input!

 

[itiwhetu]

I always run two heaters on any tank. A 6' tank I would run two 300 watt heaters a 4' tank two 200 watt heaters. Get the picture. I always like to have two heaters in a tank. I believe it makes the tank more stable. Put one at each end of the tank.

 

[itiwhetu]

For your 1000 liter tank I would run 4 x 300 watt heaters across the back wall and direct my filters to run across them. Always put the thermostat up stream to the heater.

 

[itiwhetu]

Talking Heater/ thermostats. Because I was a Bread Baker in a past life I have a very accurate temperature probe. Almost all heater/thermostats are about 3-4 degrees out. So be aware what you think you have may not be the case. I also have a multi meter that can measure temperature. Please get something that independently tests your temperature and take no notice of the dial.

 

[Ch4rlie]

I agree that the larger the tank the more heaters you require to maintain an even tank temperature.

It’s pretty much standard practice to have 2 slightly oversized heaters for larger tanks and just the one slightly oversized heater for smaller tanks.

I tend to go by the old 1W per litre rule, so if I have a 40 litre tank (10 US gals) I get a 50w heater in fact I’ve used 100w heaters for this sized tank too.

Heaters only heat up or switch on when desired temp is lower and simply stop heating or switch off once desired temperature is reached. So the higher the wattage the less energy it uses to heat up tank water. Fairly simple really.

Of course some brands of heaters are better than others, I have my own preferences to certain brands and always get one with adjustable heating control, it’s fairly common for heaters to be off by a few degrees so you have to adjust for that but it’s not a worry as long as you are aware.

Getting a decent thermometer for tank water is a must, I usually have 2 thermometers on my tanks, one at each side of tank as well as a probe that I check at various areas of the tank so I know if there are cold spots or not and adjust heater or position accordingly.

One thing is I never ever buy second hand heaters, bit of a no no as you don’t know what you’re getting exactly.

 

[Oblio]

I'd like to run 2 heaters on my 125 G, what is the best way to ensure that the heater thermostats are 'calibrated' to each other, or does it matter in practice. i.e. just use the same setpoint for each?

Added: I'm currently running an Aquaclear 110 with the existing heater near the filter in the corner. It is an old heater that came with the tank, My Thermapen shows that both sides of the tank are within < 0.5 F difference in temp, so I am mainly looking for redundancy in case of failure, especially given the age and unknown condition of the existing heater.