Heater

[vypre]

I have a spare 400 watt Heater. Would that be too much for a 40b with a 20 long sump?

[cloak]

I don't think so, but if you don't have some sort of controller just be aware that things can definitely heat up in a hurry if the unit malfunctions.
Having two 150 watt heaters would probably be your best bet though. (just in case one does in fact fail) GL.

[DrewHaus]

I don't think so, but if you don't have some sort of controller just be aware that things can definitely heat up in a hurry if the unit malfunctions. Having two 150 watt heaters would probably be your best bet though. (just in case one does in fact fail) GL.

a 400W heater on a 40b will definitely heat up quickly if it fails or is set too high. I wouldn't use it without a controller.

[vypre]

OK thanks

[cloak]

FWIW I've been using a 300 watt heater on my 20 gallon DT with a 10 gallon sump for about 7 years now without any problems. (no controller) The heater itself has been in service for about 12+ years now too. It definitely can be done.