In order to lead a long life, fish need to have a proper aquarium environment.  There tends to be a misconception that fish can lead a long and fulfilling life contained in a fishbowl with a little gravel in the bottom; for most fish, this isn’t true.  Fish need their aquarium to have a water pump, aquarium plants, and in some cases, a water heater.  Without a water pump, the water in the fish tank can become bereft of oxygen, and the fish will suffocate.  Aquarium plants can also assist with oxidizing the water, and provide a food source for some kinds of marine fish.  It’s important for certain fish to have a water heater, but most can make do with a lamp above the fish tank. 

Caring for saltwater fish can require all the above amenities and much more.  It’s necessary to maintain the right salinity level within the fish tank, and also ensure that the tank doesn’t overflow.  In addition, there are specific heat conditions that are essential for tropical fish.