Fish are cold-blooded, meaning the temperature of their body is the same of that of their environment. Since fish can’t change their body temperature it is up to the aquarist to maintain proper aquarium temperature.
All fish are different in the temperatures that they are used to, it will depend on where they are from. If the water temperature changes by only a few degrees this can be lethal for your fish. Keeping your fish happy requires you to know what temperatures your fish are used to. Temperate fish will probably not need a heater as they are from cooler regions of the world. Most fish are tropical though and need warmer waters to survive. These fish tanks will need a heater.battery operated heater for fish tank.battery powered tank heater
If you are looking for a heater you have a couple options. They can be categorized into three sections.
Hanging Tank Heaters – The simplest heaters are the ones that hang on the edge of your tank and are partially submerged in the water.
Submersible Heaters – Fully submersed heaters allow for more adequate heat exchange over partially submerged heaters. Places of high circulation are best for these heaters in such places as near a filtration system or pump.
Heating Cable Heaters – Heating cables are mostly used in freshwater aquariums but can be found in saltwater aquariums. The heating cable is placed under the aquariums substrate. Unfortunately it is a bit difficult to replace the unit because the substrate must be dug up to replace the cable.
It is good practice to equip your tank with an extra thermometer other than the heaters thermostat to make sure that your heater isn’t malfunctioning. Try to avoid thermometers made with metal or mercury. LCD strip thermometers are reliable and inexpensive. Larger tanks might need two thermometers for both ends of the tank. They will make sure that the whole tank is of equal temperature.