Heat is a factor that can adversely affect both humans and animals and if you own an aquarium you must be well aware that each type of fish needs to live in a temperature that mimics their natural habitat.
Both freshwater and saltwater fish cannot live in temperatures that are warmer than the normal temperature for their species.
Cold water fish especially have a hard time surviving in a warm aquarium water.
If the water is too warm then this can lead to the death of your fish which is something all aquarium owners want to avoid.
If you have a saltwater aquarium then it is crucial for you to remember that the margin for error is even less in a saltwater aquarium.
Even if the temperature of the water goes up by one or two degrees this can be fatal for the health of your fish.
Reef aquariums and invertebrate setups in particular are very delicate and the organisms cannot withstand warmer water than usual since these organisms are very delicate.
Both freshwater and saltwater aquariums require dissolved oxygen in the water in order to allow the fish to breathe without any problems.
Saltwater aquariums in particular contain lesser dissolved oxygen as compared to freshwater and losing more  oxygen will not be good for the fish.
Insufficient oxygen can cause fish to gasp for air and the end result may be tragic.
The main cause for insufficient dissolved oxygen in an aquarium is higher temperatures of water which cause the dissolved oxygen from the water to be let out into the air faster which causes a lack of dissolved oxygen.
Some people try running an air conditioner to help reduce the temperature of the aquarium water.
 This practice is not usually successful since the temperature has to be reduced every day for 24 hours till the hot season is over, and it is not practical and in some cases even possible to run an air conditioner for such long periods of time.
Aquarium chillers are the best option if you want to invest in equipment that will help you cool the temperature of the aquarium water and help you protect your precious and expensive fish or invertebrates.
Aquarium chillers can also help you maintain sufficient amounts of dissolved oxygen in the water as they cool down the water temperature to the desired temperature.