Temperature can vary greatly in a tropical aquarium, from 22 degrees right up to 30 degrees, depending on the species being kept, we achieve these temperatures by use of an aquarium heater, these heaters contain what is know as a heaterstat, which regulates the heat given off by the heater, and maintains it at a set temperature. Heaters can be purchased in varying forms, but the most popular are the heaters that can be adjusted by the user, these heaters are generally fully submersible and can be set and almost forgotten, as they regulate the heat for you, however it is advised to have a thermometer and check it regularly to ensure that the heater is functioning properly. We advise to change your heaters every 2-3 years to prevent catastrophic malfunction in the aquarium. It is also advisable to actually have a redundant heater in the aquarium, or at the very least in the house in case the aquarium one breaks down, this will prevent your tanks inhabitants going without heat should this happen.
Temperatures can vary species to species, Subtropical fishes often referred to as "temperate" fishes should be kept between 22-24 degrees, a common misconception is that these fishes do not require a heater, this is simply not true. Although these fishes can survive in an aquarium below these temperatures they do not thrive, much like a camel in the arctic!
Temperatures for tropical species vary even greater, depending upon the origin of the species the temperature can be as high as 30 degrees, especially for some south american cichlids and discus, however for the most part tropical species are happy at between 24-26 degrees.
Temperature consideration should be given at the initial setup stage of the aquarium, this way we can cater for the species we want to keep. Research your aquarium inhabitants before you purchase them to ensure they fit into your plans for your aquarium or your existing tank.