The Inkbird Temperature Controller is a MUST for aquarium redundancy. Not only does it display accurate temperature at a glance, it actively controls your heating and cooling equipment to maintain a steady temperature. It also has a visual and audio alarm should your water rise or drop outside of the set temperature window. 4/5 Easy to use is because the initial setup is a bit lengthy as it starts the temp setup at ridiculous temps. I had to inch my way from -40oC to 24oC. Highly recommend. Spend a few bucks for a great little device that prevents costly tank crashes.