Yeah, I've heard they are, but then I've also heard that cycle contains say the boost of nutrients or bacteria that support and encourage the growth of the nitrosomas[?] and since these bacteria need to eat and have temperature requirements, the cold keeps 'em in a state of lets say hibernation until you dump it in the tank and bring it up to temp where they wake up and require ammonia to feed the nitrogen cycle. If cycle contains this same bacteria I would think it would die off without the ammonia to feed on since at at least room temperature this bacteria would then be active and need to feed while still in the bottle.