My gerbil?

I have two gerbils and a decoration for the tank of my aquarium. One of the gerbils is very active in the bottom, where the bedding is. The other is up top all the time. Is this correct or should I worry?

It's probably just a little afraid of the one below to keep it up. When one is tired down the above is probably better. Also, the above might want to leave the cage.

Gerbils Aquarium

Mr. Heater MH12T Single Tank-Top Propane Heater $45.34 If you’re looking for simplicity and convenience in an outdoor-only heater, the Mr. Heater MH12T 8,000-14,000 Btu single tank-top propane heater may be the answer. As the name implies, this unit mounts directly to the top of a five- to 20-pound propane cylinder (sold separately). To allow you to choose between conserving fuel or kicking out more heat, the MH12T has three settings, Hi (14,000 Btu),…