I've got my 2.5 gallon nano cycling, and currently have a top fin heater inside the tank. The top sticks out by about 1" to 1.5". Does anyone know where to find the smallest possible heater which sports a temp control? I'd like to find one around 4" inches so that it will fit in the media basket area of my Aquaclear 50. Have had no luck looking. Would be nice to open up the back corner of the tank. TIA.