Question: can you put a heater in a 1 gallon fish tank?
Answer: Although it's rated for tanks as small as 0.5 gallons, we don't recommend using a heater on any tank under 1 gallon (or keeping a Betta in a tank that small). This heater will also work on tanks larger than 1.5 gallons, although it will maintain a temperature below the set 79 degrees when used in a larger tank.