The best aquarium heater … De-icers and heaters … So, when you think of an intelligently designed heater, one of the heaters that should readily come to your mind is the SZELAM Smart Mini Aquarium Heater. Another name on our list of 7 best heaters for betta fish is the Szelam Smart mini heater. Picking the appropriate aquarium heater is a critical thing in maintaining a comfortable and healthy aquarium. This heater… You need to decide whether you want a heater, de-icer, or both. This ensures that your pet fish will live in a happy and comfortable environment. Again, it depends on your needs. Different fish require different water temperatures, so ensure the water in your aquarium is perfect for your fish with this Hygger 500W 300W Aquarium Heater.This is a fast heating submersible thermostat heater suitable for a goldfish tank with a volume of between 30 and 120 gallons.. Floating heater and de-icer will operate mainly on or near the surface of the pond, and devices such as this are really more suited for de-icing your pond rather than heating. Speaking of intelligence, the heater… The Rena Smart heater comes with 2 metres of cable and is suitable for freshwater or marine aquariums and comes complete with a double suction cup attachment so you are able to safely attach the heater to your aquarium …