newb question alert!!

i am looking at a way to control the temp of my brew prior to going into winter and i am considering 2no options.
The first is a brew fridge which is quite well discussed on here and relatively simple to create.
The second is using a trug and aquarium heater.
I have the new coopers vat with the tap on the front. looking at this the other day, i would expect to have only the first couple of litres within the fv in the water in the trug without the trug water touching the tap. Would this be suitable for maintaining a temperature or do you need to have more water in the trug?
I have read of people half filling the trug with water for the heater to operate in but this would submerge the tap.
In that case, how do you accommodate the tap?
i assume that you could add some steriliser to the trug water and let it cover the tap but would that be acceptable and if so, would you need to change the water every so often?
I look forward to your responses.
Barry