I just opened a new Fluval M100 heater last night…stuck it in the tank and plugged it in. The blue pilot light lit up and I went to bed. This morning the water is still cold…pilot light is out and heater is set 72*. I took heater out of it's holder and pilot light turned by on…secured heater and light stayed on for about 20 min. Now it is out again. Is there a trick to this? Do I need to add warm water to get it near 72 then the heater will take over?