I have read a couple of threads lately withppl worying about there tanks getting too cold during prolonged power outages i have a sugestion buble wrap no dont laugh ot is used in glasshouses to keep plants warm so why not our fishies first of all you need the big one the one that is 10-12mm thick then you spray a fine mist of water on the glas and place it on boble side towards the glass as long as the glass was crean befor you did it it will stick for a long time i have heard reports of 5 years on some glasshouses you can also use it on youre house windows if you cant aford double glasing this has the same efect but a lot cheeper