Betta Bowl Slim Fish Tank Heater, 7.5-watt, measures 3.5 inches round, black; For tanks 2-5 gallons

Hydor Betta Bowl Slim Fish Tank Heater, 7.5-watt, measures 3.5 inches round, black; For tanks 2-5 gallons

Penn-Plax Therma-Temp Temperature Sensitive Thermometer | Great for Checking The Water Temperature in Smaller Tanks | Small Strip, 2" (DT014)

PAIZOO Fish Tank Digital Thermometer Accurate LED Display to ±0.9°F Tank Thermometer Aquarium Temperature Measurement Suitable for Fish, Axolotl, Turtle or Aquatic