Finally got the spawning tanks alarm system installed to protect the precious broodstock from equipment failure.  It’s quite a simple system that uses an Arduino Uno to measure the airline and waterpipe pressure.  If air or water fail (i.e. blower or pump fail, pipe work fails or power outage) the pressure drops.  The Arduino will detect this and alarm.  My son Nick programmed the Arduino in C and I knocked up the hardware.

Because the environment in the spawning facility is very humid the alarm is in a waterproof case and I have used internal reed switches that can be controlled with a magnet without having to open the box!

Excluding time, the project cost less than $200