Abstract: An apparatus for inhibiting bacteria growth and reproduction in an aquarium containing water and aquatic organisms such as fish, includes at least one positive and one negative electrode connected to a D.C. power source operative to produce electric power in the range of about 1.5 to 3.0 volts and about 0.1 to 10 milliamperes. The electrodes are disposed in spaced relation within the aquarium, and are at least partially immersed in the water. The positive electrode is formed from galvanized wire or zinc wire, and the negative electrode is formed from galvanized wire. The electric potential between the electrodes is effective to inhibit the reproduction of bacteria which is detrimental to fish, humans and water clarity. In larger aquariums, a plurality of pairs of positive and negative electrodes are spaced in alternating sequence within the aquarium to maintain an electric potential throughout the aquarium effective to inhibit bacteria reproduction.