skip to main content, skip to Quick links, or skip to Search

main content

Dealing With a Power Outage: Aquariums and Ponds

Millions of residents in numerous states are without power following the destructive force of Superstorm Sandy. Many of these individuals undoubtedly own aquariums filled with valuable fresh or salt water fish. With restoration of power perhaps several several days away in some hard hit areas, what should an aquarium owner do? Dr. Greg Lewbart, professor of aquatic, wildlife, and zoologic Medicine at NC State College of Veterinary Medicine, offers some advice.

By Dr. Greg Lewbart MS, VMD, Dipl. ACZM

In the In December 2002 the numerous cracking boughs and fiery transformers awakened me to the importance of a contingency plan for pet fish when electricity stops.  Much of this information applies to power outages regardless of the cause. Please feel free to pass this document along to anyone that may benefit.

General Guidelines

Food:  Do not feed your fish during a power outage.  In warmer months the act of eating and digesting will use valuable oxygen.  In winter your fish will likely have plenty of oxygen but will probably be uninterested in food with a slowed metabolism.  Furthermore, uneaten food will only pollute the aquarium or pond with unnecessary nitrogen.

Temperature:  In winter, try and insulate your aquarium with a blanket, sleeping bag, or newspapers.  In summer, remove anything from the surface of the water in an effort to increase the surface area and hence gas exchange efficiency. Obtain an aquarium thermometer and have it handy to monitor the water temperature. Most tropical fish can tolerate temperatures in the low 60’s(F) or even high 50’s for several hours. Once temperatures dip to the mid-50’s action should be taken to elevate the temperature. Here are some options:

Temperate species such as goldfish, koi, and North Carolina native fishes should be fine without changing anything in the environment. If the power outage persists and the surface of a pond freezes over, the ice can be mechanically broken to form an “air hole.”

Only as an absolute last resort should fish from one aquarium or pond be mixed with fish from another aquatic system. This practice greatly increases the risk of spreading infectious viral, bacterial, fungal, and parasitic diseases. It may also lead to inter or intraspecific aggression.

Water Quality: The longer fish remain in unfiltered water the worse water quality parameters will become.  Again, do not feed fish while there is no power and try and test the water for elevated ammonia levels.  Most fish can survive days or even weeks without food. If ammonia levels increase above one (1.0) ppm then water changes (10-30%) are recommended.

Lighting: The least of your worries. Ornamental fish will survive indefinitely without fluorescent/ supplemental lighting. This is of more concern with tropical reef aquaria where live sponges and coral are maintained.  Many of these invertebrate species rely on bright light and the symbiotic organisms the light supports.

Supplies to have available:

Zip-lock bags (various sizes)

A net (note:  herding fish into a plastic bag using a net is a much safer way to capture fish than using a net on its own.  Nets can damage the protective mucus layer and sensitive epidermis.) 


Propane or kerosene heater

Watch Dr. Lewbart on Nova ScienceNow conduct fish surgery

Oct. 30, 2012