This small and effective heater will warm your aquarium with a constant heat output, always heating to 5°C above ambient room temperature. The flexible fitting system lets you choose where you place it - under gravel at the bottom of your tank, tuck it away in your filter or pop it on the side of your aquarium. No matter where you choose it put it, the neat flat design is super discreet. It's the perfect solution for aquariums up to 20 Litres (4.4 gallons). An easy-read thermometer strip is included to stick to the outside of the aquarium.