Heater placement

[Crocodylus]

Where is the best place to put a submersible heater in relation with a power filter?
Is it at different ends? Is it under the filter intake? Is it close to the gravel?
All this for a 30G-50G setup using an EBO and a Penguin 330

Thanks in advance

 

[Andy16]

I would put the thermometer far away from it so you get more accurate readings. I would put it close to the filter intake tube so that more water passes near it. Then the heated water would get mixed in with the other water by the overflow.

 

[NJ Devils Fan]

If you have 2 filters on a 55g tank, I would put 2 smaller heaters horizontally near the filter intakes. I would get 2 150 watt heaters.