Heater for 10G divided?

[Marvelous1]

Hey guys I used to post here under the name Marvelous but I can't sign back in to that name so had to start a new one.

Anyway, on to the issue. I have a 10 gallon divided tank with 2 males and a nerite snail. The thermometer apparently malfunctioned because the water's cold, but temp reading is 75. I originally had 2 little heaters (one per side) since that is no longer working I need to know what to do here. 2 little heaters again or a big one. The water is pretty calm, I have a baffled filtered on one side. I'm afraid of creating a hot spot with the heater on one side. Advice needed! I can try to attach some pics if that helps

Thanks in advance

[aemaki09]

It'd probably be cheaper just to get a 50 watt heater. I have a top fin one from petsmart that was pretty cheap and works AMAZING. I have my 10g divided 4 ways, with only a sponge filter for any water movement, and the heat gets to all corners of the tank even through 3 dividers.