Amazon has Fluval Edge Digital Aquarium Thermometer for $1.39 with free Prime shipping. No minimum.
https://www.amazon.com/dp/B002LL2…PDKIK
Select no-rush shipping at checkout to receive a no-rush shipping credit.
- Accurate and easy-to-read thermometer
- Mounts easily on outside of glass
- Ideal for fresh and saltwater tanks
- Temperature range of 64 to 86 degrees Fahrenheit