Did you measure voltage or current (amps)? If you register a flow of current through the system it could cause some problems with the corals. If it's simply voltage, this is normal. Voltage is only the potential for electricity to flow, and is found everywhere. I once read there is a 300V difference from your head to your feet. If there is current flowing be careful with it. It only takes 0.1 amps to kill a person. It's unlikely to kill a person, but still is possible. I'd imagine if it can kill a human it can probably toast a coral.