At What Temperature Should I Keep My Saltwater Aquarium?

When you expose fish to water parameters other than their preferred conditions it stresses fish. Stressed fish may suffer from disease, tissue damage and low oxygen. Marine fish are more particular than freshwater fish about their water parameters, including temperature. Many prefer warm water, others thrive in cold water. Even among warm-water species, you must ensure you the temperature is appropriate for all the specimens in your tank.

  1. Tropical Aquariums

    • The vast majority of marine aquarium fish and invertebrates come from the tropics, as do popular reef organism like corals and crustaceans. Tropical ocean water has very stable water temperatures, ranging from 72 to 78 degrees Fahrenheit. It's important to avoid sudden swings of temperature, even in their appropriate range. Changes toward ideal conditions can stress fish and inverts. You need to pay special attention that new water is the same temperature as the extant water when doing water changes, since it's easy to cause sudden fluctuations.

    Cold-Water Tanks

    • While most saltwater fish and inverts hail from the tropics, cold-water tanks are gaining popularity. These new aquariums feature fish from temperate and subtropical waters, waters usually colder than room temperature. You may need to invest in chillers to keep these organisms healthy. Most of the coastal regions of the United States and Europe fall into this category. Cold-water aquarium fish and inverts are diverse in terms of their ideal conditions, but generally most will thrive between 50 and 60 degrees Fahrenheit.

    Heaters

    • For most fish, you will need to keep the water warmer than room temperature. To figure out how much heating power you need, consider the volume of the aquarium and the wattage of the heater system. For small aquariums you actually need more heater power, since smaller tanks lose heat faster. For aquariums under 50 gallons, you need 5 watts of heater power per gallon of aquarium volume. Aquariums larger than 50 gallons generally need only 3 watts per gallon. It's best to distribute wattage among multiple heaters; if one fails, you can keep the tank warmed until you can replace it.

    Chiller

    • A cold-water aquarium needs a chiller to maintain temperatures lower than room temperature. Chillers are expensive because of the metal in their heat exchangers; most metals corrode when exposed to saltwater, leaving only costly metals like titanium as options. Tropical tanks may benefit from chillers, since aquarium lights can overheat them and endanger fish.