Troubleshooting Stray Voltage in a Saltwater Aquarium

Saltwater Butterflyfish in an Aquarium


Darya Bystritskaya / EyeEm / Getty Images

Putting electric appliances, such as heaters and powerheads, in freshwater can cause electrical problems. But when you add the corrosive effects of salt to the equation, the potential for electrical problems increases dramatically. Even salt creep can cause corrosion in metals.

Fortunately for saltwater aquarists, electrical equipment sold for use in an aquarium is of high quality and seldom fails. However, if an appliance does fail and leaks electricity into a tank, it is called "stray voltage." This stray voltage, even in small amounts, can cause several subtle or dramatic problems in an aquarium. Below are some possible concerns.

Head and Lateral Line Erosion

Head and Lateral Line Erosion (HLLE) disease appears as open pitted wounds around a fish's head and along the lateral line, as if something is slowly eroding away the flesh. Many different causes of HLLE are being investigated but some anecdotal evidence in ocean fish has shown a link between certain environmental factors and the onset of the disease.

Sudden Death of Tank Inhabitants

Sometimes, aquarists have tested for stray voltage leaks in their tanks after experiencing sudden and otherwise inexplicable losses of fish and found that a faulty appliance in their tank was the cause. There have been faulty aquarium heaters on the market that have resulted in the complete loss of all fish and invertebrates in saltwater aquariums. Some manufacturers have recalled equipment and refunded aquarium owners but the aquarists with the faulty heaters would have preferred that the incidents never happened. Detecting the voltage leaks at an earlier stage could have prevented the disaster.

Unusual Behavior of Tank Inhabitants

When continuous strange behavior such as a rapid and jerky swimming pattern or frequent quivering of tank inhabitants is observed, many aquarists have discovered that the cause was stray voltage. Fish have sensors on their bodies, such as along the lateral line and on their noses, which are sensitive to changes in electricity in the water around them. When these sensors receive a continuous supply of abnormally high electricity, it throws their systems out of kilter. An example of how this has been put to our advantage is in the "shark repelling" devices for swimmers and surfers that have been developed. These devices emit a small amount of electricity into the water around the swimmer/surfer, which the sharks pick up as they approach, find that it makes them uncomfortable and so they swim away.

How to Test for Stray Voltage

  1. Purchase or borrow a voltage meter. They can generally be found for less than $20 at most automotive parts or hardware stores.
  2. Turn the selector to "120 AC Voltage."
  3. Insert the tip of the black probe into the third or "grounding" hole in an electrical outlet.
  4. Insert the metal tip of the red probe into the aquarium water.
  5. Watch the meter needle for any movement. Any needle movement indicates a voltage leak in your system. Digital meters will show a number reading.
A voltammeter
Caspar Benson / Getty Images

How to Identify the Voltage Leak Source

  • One at a time, disconnect each electrical appliance (heaters, pumps, lights, chiller) associated with your aquarium, retesting for voltage as described above after each unit is disconnected.
  • Heaters and water pumps (powerheads) are the most frequent cause of voltage leaks. These devices have 120 volts of electricity feeding into them, which is enough to do a lot of damage in a saltwater aquarium.
  • When the damaged electrical device is found, disconnect it from the electrical circuit carefully. Keep your hands out of the aquarium and don't handle equipment with wet hands in order to avoid electrical shock.

How to Solve the Voltage Leak

  • Replace (recommended) or repair the faulty unit. Test the aquarium water once again to make sure that you have eliminated the problem.
  • Install a simple grounding probe in the aquarium to avoid damage to the inhabitants. These are available at aquarium stores or online aquarium supply companies for under $20. This may temporarily take care of the symptoms of stray voltage, but it does not cure the cause of the problem.

Many aquarists test their tanks for stray voltage regularly as a part of their normal tank maintenance routine. Detecting a voltage leak problem in its early stages can help eliminate or reduce problems in the future.

Article Sources
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Aquarium Heaters Recalled by United Pet Group Due to Fire and Laceration Hazards. United States Consumer Product Safety Commission.

  2. Fish Electrocution. University of Guelph.