Can't keep constant Temp!!!

Sep 23, 2016
I am having serious issues maintaining a constant temp in my 20 gal and my 65 gal. I have Aqueon 200w and 300w. Here is the frustration. Ex) Temp is set at 80 degrees. Lets say the room is at 80, The heater is running bringing water temp to 84-86 degrees. There is no reason the heater should be on!!! I fooled around with the dial because I know it isn't "exact" do to the design but then I am just going in circles with it.
Both tanks are acrylic with same brand of heaters. My question is what is the BEST heater out there to maintain constant temps? Please help!


Superstar Fish
Jan 11, 2013
East Aurora, NY
200w is a BIG heater for a 20g tank. It depends on how cold the room gets that the tank(s) are in, but I wouldn't use more than 100w in a 20g tank., I use a 200w in my 55g and a 250w in my 75g. That might be part of your problem.

84-86F is pretty warm. You should gear the water temps to the fish you keep. I tend to go towards the low-end for temps. For danios, most prefer cooler temps 72-74F.

Even my Oscar and Severum tank I keep below 78F.