# How many heaters/watts for 125 gallon

#### gray_matter16

I have a 6ft long 125-gallon freshwater planted aquarium. It currently is a species only tank with 8 german blue rams. I want the tank to be 80 - 82F and possibly up to 86F. I currently have two 300w heaters placed at either end with pretty good circular flow. We live in a bi-level house in Michigan and the aquarium is in the lower level. So the room is halfway underground, and as such, the ambient temperature of the room in winter is 60 - 63F.

I know there is maths involved between the target temp, ambient temp, gallons, and wattage necessary to raise the temp. I'm here to learn what that maths is? Because currently I have both heaters set to 86F (or so the dials say), and the tank only reaches max 79F (says my thermometer whose sensor is placed in the nearly exact middle of the tank). Should I increase my heater's dials, get an additional heater, or something else entirely? Help much appreciated.

#### BigManAquatics

I usually go by 5 watts for each gallon. Since you already have 2 300-watt heaters i personally would add a 3rd heater at 200 or 300 watts, spread the load. Just curious, what is usually room temp at your house?

#### gray_matter16

I usually go by 5 watts for each gallon. Since you already have 2 300-watt heaters i personally would add a 3rd heater at 200 or 300 watts, spread the load. Just curious, what is usually room temp at your house?
Depends on the season. In the winter we have the thermostat, which is on the upper level, set to 68 during the day. So the upper level is 68 while the lower level is 60-63. In the summer the thermostat is set to 75 and the lower level is about 68-70

#### TClare

I would first turn up the dials on the heaters and see if it reaches the temperature you want. (the dials almost never correspond to the real temperature and it takes a while to get it set right). If you then see that your heaters are on all the time, it may be better to have an extra one. Otherwise stick with the two x 300, I think they should be enough.

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