A typical reef-pi build involves both water and electricity, this can be potentially hazerdous. Please ensure safety consideration for yourself and all the living things in your tank. If you are working with electronics, especially with water and high voltage together, it can be dangerous. This page is intended to inform you about this risk. It is not high voltage but high current that imposes risk. High current here stands for milliamps.
Most of us aware that Higher voltages can be fatal. Salt pollutes the water (electrically) and brings down the resistance. This allows even lower voltage to be fatal. Take appropriate safety precautions.
Above all, your safety is your own responsibility, including proper use of equipment and safety gear, and determining whether you have adequate skill and experience. Power tools, electricity, and other resources used for reef-pi builds are dangerous, unless used properly and with adequate precautions, including safety gear. reef-pi project authors disclaims all responsibility for any resulting damage, injury, or expense. It is your responsibility to make sure that your activities comply with applicable laws, including copyright. Always check the webpage associated with each project before you get started. There may be important updates or corrections!
Last, but not the least, The United States Fire Administration (USFA) has a guide and many simple steps you can take to prevent the loss of life and property resulting from electrical fires.