Electrolysis is the use of an electrical current to split compounds, including water, in various ways.
The energy or 'pull' created by positive and negative forces from a set of charged electrodes is enough to break down the bonds that hold water together. In freshwater fishkeeping, electrolysis is becoming an increasingly popular way to provide carbon dioxide (CO2) for plants.
The process works by water between two electrodes firstly being split by electrolysis, producing oxygen and hydrogen (2H20 = O2, 2H+, 2H-) Between the two electrodes is a block of carbon, the oxygen produced bonds with the carbon, producing carbon dioxide (02 + C = C02).
The effect can be seen as a fine cloud-like production of bubbles, which is a combination of hydrogen and carbon dioxide.
The carbon dioxide is assimilated by plants or released into the atmosphere along with the hydrogen. Providing CO2 by electrolysis is becoming increasingly popular as it is easy to control via a simple plug timer, and involves no chemicals or pressurized containers.
The carbon blocks used in these units are specifically designed for this use and will need occasional replacement, which can be a little costly, but still comparable to other methods.