Hi, I know FBT's are generally regarded as not needing heating, and are fine at room temperature, but what really is the coldest they can safely get down to?I have my FBT tank in my lounge, and what with the recent cold snap we're now getting in the UK, the thermostat in the lounge is reading a temp as low as 15C overnight. I anticipate this could get even colder, especially when winter properly sets in, and it can get down to 11C or so - it did last year. So I'm wondering how cold my FBT's can be allowed to get, if this is too cold then I need to look for a suitable heater to keep the water part warm for them.