If they made 3 gallon coffee pots...
It looks cool but yeah, it's really too small. However, if they made 2 or 3 gallon coffee pots that were clear I might do that...adding a filter and heater of course. It's a cool idea but not the best for the fish.
EDIT: like I said, it's too small to do this but if they made giant-size coffee pots...
You could have a filter intake, build the filter into the upper part where you put the water and coffee grounds and have the output where the coffee normally comes out! XD
My plans are perfect, they just need larger scale... :DD