I am brewing my first batch of mangrove jacks stout (extract pouch) in a stainless steel fermenter. Ive noticed that when the temperature drops sometimes the pressure drops as my airlock liquid indicates. Ive been putting a heater on it but the second i switch the heater off or move it further away the pressure seems to drop instantly. Ive been trying to keep it around 22 degrees C but its quite costly to keep the fan heater on 24/7. Generally it hasnt gone below 18 degrees C even with out the heater. Any suggestions? Im 5 days in.