Grade Levels
9-12
Objectives
• Students will set up a tank with a live knifefish to study its
electrical discharges.
• Students will discover how knifefish use electricity to
navigate and communicate.
Time
Two 40-minute periods
Group Size
Whole class discussion and demonstration
Materials
Available at tropical fish stores:
• Aquarium kit (includes the tank, filter, pump, hood, water
testing supplies, instructions on easy setup and
maintenance)
Note: a general rule of thumb for the number of fish you should put
in the aquarium is one one-inch-fish for every gallon of water. For
example, if you are planning on keeping only the knifefish, a 10-
inch fish would require a 10 gallon tank.
• 1 fishnet (this electric fish will not shock you! But it’s easier
to handle them with a net than sticking your hand inside
the tank)
• a knifefish; approximate cost $15.00
• small portable aquarium or acrylic Critter Keeper
• a rock
• an aquatic plant
Other supplies:
• 1 small audio amplifier; approximate cost $12.00
(e.g. RadioShack part #277-1008 www.radioshack.com)
• 2 bare copper wires
• 2 alligator clips
• a small magnet
• a bar magnet
• 1 tablespoon of iron filings
• Ziplock sandwich bag
Activity
Electric Fish
Summary
In the deep dark waters of the Amazon River, there is a
whole order of fish that communicate with each other
using electricity! Students will learn how these electric
fish create electric fields around them to send off signals
and perceive the world around them.
Electric Fish
1
Background Information
Any fish that can generate electric fields is considered an
electric fish and is classified as electrogenic. If a fish can
detect electric fields, then it is said to be electroreceptive.
Most fish that are electrogenic are also electroreceptive.
Fishes that can only sense electricity are usually not
considered electric fish in the true sense.
Strongly and Weakly Electric Fish
Fish that have an electric discharge that is powerful enough to
stun their prey are called strongly electric fish. The amplitude
of the sig