Best Seller | Aquatop Pisces Nano Preset Aquarium Heater for Fish Tanks up to 8 Gallons 25 Watt PCS-25W Aquatop s PISCES Nano Aquarium Heaters. The compact design allows for versatile placement in small aquariums such as our PISCES All-in-One Aquariums. Each unit has a built-in electronic thermostat pre-set to 78 degrees Fahrenheit for precise... more | | $18.99 $15.99 go to store |