This heater is perfect for small tropical fish living in glass or acrylic desktop aquariums that are between 1 and 10 gallons. No need to worry about complicated installation - this little guy is fully submersible and comes with suction cups that allow for vertical or horizontal placement on the bottom or side wall of your aquarium. And don't let its size fool you - with 5 watts of power, this heater efficiently warms up your aquarium water.