This morning my tank got extremely cold.  Like, down to 55-60 degrees!  Obviously, way to cold for my fish.  So, my question is can I turn on the heater in the tank with a hillstream loach in it?  Or will it burn the little guy?  I usually don't have to use it, the tank just tends to stay warm, even in winter.  So, is it safe?  Should I take the risk?  Or should I move the little guy to a small tank attached to the big one until it gets warmed up?  Thanks!