What size heater 🤷🏼‍♂️🤷🏼‍♂️🤷🏼‍♂️

[Trailblazur]

I know Cory says he doesn’t go by the industry standard when sizing heaters for an aquarium. 

What rule of thumb do y’all use when deciding on heater size?

[nabokovfan87]

This is generally what I use.

[Pepere]

I much prefer something along the lines of Aqueons guidance than Cory’s insofar it takes in to consideration heat loss from the tank better.  Ie the colder your room the tank is in the greater the heat loss.

That being said, I would advocate initially erring on the lower side of the equation..  you can always add an additional heater to the tank at the opposite side if the lower size option is proving insufficient.  Having two smaller heaters have a host of benefits and only one negative.  The negative is added cost to purchase vs 1 single larger heater.  Well maybe another negative as you have another current carrying wire immersed in your aquarium…  and more visual clutter…

 

The benefits in my estimation outweigh the cons.

1.) Better heat distribution opposite ends of the tank

2.) reliability redundancy.. If one heater fails in always off position the other heater keeps the tank warmer than if you only had one heater that failed to add heat.   And if one heater fails in the always on position it is less likely to cook your fish.

I have Inkbird controllers on my tanks as well and only use the heaters temp limit as a failsafe to prevent overheating.  The inkbirds are set for a 2 degree differential range.  Ie, they turn on power to the heater when water temp drops below 74 degrees and turns off power when it gets up to 76 degrees.  This causes the heaters to have less number of cycles of heat yet when they run, they run longer each time.

 

as far as practicality, I originally had 2 50 watt heaters in each 29 gallon tank and a 50 and 25 watt in my 20 high.  These are located in my bedroom which is very well insulated, R30 walls, air sealed, insulated windows.  I only heat the house to 55 in the winter, but I keep the bedroom closed except when goin in and out.  With 80 gallons of water in the room, I run a small dehumidifier in the room set to maintain 50% humidity.  As a dehumidifier pulls moisture from the air it liberates a fair amount of heat.    As such, as cold as it gets outside, my bedroom maintains 74 degree air temp from heat loss from the aquariums to the room and the dehumidifier.  
 

I upgraded my heaters to the co ops 50 watt heaters and only run 1 heater per tank.  Perfectly adequate.  My Inkbird has a large prominent digital readout that I would quickly notice if a co op heater would fail to turn on and heat the tank.

I upgraded to the co op heater as it sits low in the tank and looks better than older tube style heater and allows me to do a water change without having to remember to turn the heater off as water level never drops below heater height.

In addition to the 50 watt heater, the tank has a 10 watt motor pumping water through the tank 24/7 which is adding 10 watts of heat all of the time.  And the lights are on for two 5 hour periods from 4-9 morning and night which adds significant heat to the tank as well, though certainly much less than the incandescent bulbs I ran on a tank when I was very young in the early 70s…

I plan on a 75 gallon in my living room after I renovate it.  I am planning on gutting the walks removing lathe and plaster and sawdust insulation, and upgrading insulation to R30 rockwool from existing R 5 sawdust… and new sheetrock.  Once done I am planning on 2, 50 watt heaters for the 75 gallon tank.  I suspect that will be more than adequate, but I will watch it closely until I gain confidence.  I will have a backup 50 on hand to add if the two struggle to maintain.

 

 

Edited May 30 by Pepere

[Hoi Polloi]

Some more information.

Aquarium Heater Size Calculator

https://thepetsupplyguy.com/aquarium-heater-size-calculator/