here is how to test with voltmeter :
- Purchase or borrow a voltage meter. They can generally be found for less than $20 at most automotive parts or hardware stores
- Turn the selector to "120 AC Voltage."
- Insert the tip of the black probe into the third or "grounding" hole in an electrical outlet
- Insert the metal tip of the red probe into the aquarium water
- Watch the meter needle for any movement. Any needle movement indicates a voltage leak in your system. Digital meters will show a number reading.
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 (power heads) 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.