I am going to order a heater for my 5ga and wanted to know if I could put the heating eliment in my hang on filter to help evenly distribute the warm water?
If it will fit it should be fine. If the heater is in the tank it will still distribute evenly. Hot water rises so putting a submersable heater at the bottom of a tank actually creates more currents in the water.
A lot of people put a lot higher watt heaters in their plastic sumps.
Personally I would keep it in the tank. The water in the filter is exposed to the air right after it would be heated, could loose heat faster that way.
There is still the possibility of it shorting out. A 5g filter isn't all that big and while a 5g heater isn't either, I don't think it's a safe thing to do. Besides, as mentioned, a 5g is realtively easy to warm evenly.
