2 x 100W should be ok for a 40G tank assuming that your ambient room temperature is no more than like 8 degrees cooler than the temperature you want to keep the tank at..
2 x 125W (or 150)would be better if you keep your room temp around 68-70..
And yes you set them at the same temp and I would recommend a controller like an inkbird blue.. Heaters are known to fail.. Having them run on a controller is a good way to help ensure that when the heater temperature controls fail it doesn't overheat your tank.
Inkbird blue is like $30 and you can plug 2 heaters right into it..
https://www.amazon.com/Inkbird-Temp...&sr=8-1-spons&keywords=inkbird+aquarium&psc=1
I wonder what will happens when controller fails? Thats a single point of failure.
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I wonder what will happens when controller fails? Thats a single point of failure.
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If heaters thermostat fail controller shuts them off..
If controller fails.. heater thermostat shuts them off..
two points of failure would be required to cause problems..
Typically I recommend setting the heater thermostats just slightly higher than the controller.. First so that they don't shut off before the controller tells them too and second so that if you check and see that the temp is a bit higher than it should be you know the controller failed..
It's a single point of failure if the controller fails to turn on your heaters. You have much more time to save a cool tank than an overheated tank, but it's still a single point of failure. Having said that, I have no problem trusting the inkbird.
I'm curious. What was the reason?There is no way to entirely eliminate the possibility of failure. All you can do is to provide redundancy for the things most likely to fail. Heck, I run three independent switches for my ATO, yet I still had a problem once with the entire volume being dumped into the tank. Reason was almost unbelievable.
I am searching for solutions to my thermostat(s) being unreliable, resulting in Temp. fluctuation in the tank. I like the idea of the CONTROLLER that can take 2 heater inputs, but if I'm going to invest in a controller, might as well have one with an alarm.2 x 100W should be ok for a 40G tank assuming that your ambient room temperature is no more than like 8 degrees cooler than the temperature you want to keep the tank at..
2 x 125W (or 150)would be better if you keep your room temp around 68-70..
And yes you set them at the same temp and I would recommend a controller like an inkbird blue.. Heaters are known to fail.. Having them run on a controller is a good way to help ensure that when the heater temperature controls fail it doesn't overheat your tank.
Inkbird blue is like $30 and you can plug 2 heaters right into it..
https://www.amazon.com/Inkbird-Temp...&sr=8-1-spons&keywords=inkbird+aquarium&psc=1