Choosing the Correct Temperature for a Marine Aquarium

To keep your marine tank healthy, you need to keep an eye on the water parameters including the pH, salinity and chemistry levels. In addition to monitoring pH and salinity levels, maintaining a stable temperature in your marine tank is one of the top priorities of aquarium owners. It's not only the fish in your tank you need to be worried about in keeping a perfect temperature, either. Corals are especially susceptible to sudden temperature changes and could be killed before you even realize the need to make a correction. Read more to learn about the ideal temperature ranges for different marine tanks.

Marine aquariums can be lumped into several categories based on their inhabitants (fish only, fish only with live rock, or reef tanks) and also by water temperature (warm water vs. cold water). Before investing in a saltwater aquarium, it is a good idea to decide which type of tank you want and to learn the requirements you will be responsible for meeting and maintaining. In this article you will learn the basics about the different types of marine tanks and you will receive tips for maintaining those tanks at the proper temperature.

Types of Tanks by Occupants

Below you will find a list of the three types of marine tanks based on the type of occupants in them. You will also receive an overview of each tank type.

Fish Only – A fish only tank is exactly what it sounds like – a tank in which the only living inhabitants are fish. These tanks are designed to showcase the fish so they are often sparsely decorated with just a few coral replicas or coral skeletons for decoration. Some of the best hardy marine species for use in fish only tanks include tangs, damselfish, and other captive-bred species.

Fish Only with Live Rock – A fish only with live rock (FOWLR) tank is a stepping stone between the fish only tank and a reef tank. In this tank you will find live fish but the decorations are living as well. Live rock consists of fragmented pieces of old reefs that have been colonized by bacteria, sponges, and other invertebrates. Live rock provides an excellent foundation for beneficial bacteria in a marine tank and it greatly enhances the tank’s appearance as well.

Reef Tank – A reef tank is one of the most challenging types of aquariums to cultivate because not only do you need to keep your fish alive, but you must cultivate a delicate balance in your water parameters to keep coral alive as well. In reef tanks the coral and invertebrates are usually the stars, even if there are a few fish included.

Types of Tank by Temperature

Below you will find an overview of the two tank types divided by temperature.

Warm Water = Saltwater aquariums that house fish from temperate or tropical climates will generally require a temperature range between 75 and 85 degrees Fahrenheit. Before settling on a temperature, research the needs of the species of fish you intend to introduce into your tank (if any), as well as the corals and other invertebrates, to see what their needs are. In this type of tank setup you will need to invest in an aquarium heater to maintain a stable water temperature within the desired range.

Cold Water = Cold water marine aquariums, though less popular than warm water tanks until recently, generally require a temperature range between 50 and 65 degrees Fahrenheit. To achieve this temperature range, it is often necessary to invest in an aquarium chiller that can be set to keep the water within a degree or two of a certain goal. In this type of tank setup, you may not even need an aquarium heater – the aquarium chiller will perform the function of regulating tank temperature.

Tips for Tank Temperature by Type

Below you will find tips for maintaining the proper temperature of different marine tanks based on the type of tank you have – fish only, FOWLR, or reef.

Fish Only (FO) = If your saltwater tank is home to fish only, all you must do to determine the proper temperature range is research the needs of the fish you plan to introduce into your tank. If you plan to house several different species it is important to select those that have similar needs, especially when it comes to tank temperature. Generally, saltwater fish from temperate and tropical climates require temperatures between 75 and 84 degrees Fahrenheit to thrive.

Fish Only with Live Rock (FOWL) = Again, the correct temperature range for a FOWL tank will depend on the particular fish you intend to house. Live rock does well in a wide range of aquarium temperatures, so rely on your research to determine the temperature which is best for your fish. Try to avoid housing fish from very disparate environments in the same tank because their environmental requirements may not be compatible.

Reef Tank = The average temperature for reefs in the wild is around 82 degrees Fahrenheit, though corals and other reef tank inhabitants can do quite well in 70-degree temperatures. Reef tanks in which marine corals are housed should be kept no lower than 65 degrees because warm water corals cannot develop in temperatures this low. The same is true of fish and other organisms that come from warm water environments - temperatures above 75 degrees Fahrenheit are necessary for fish to develop and metabolize properly.

How to Maintain the Temperature of a Marine Aquarium

Aquarium heaters and chillers are the most effective ways to maintain a stable temperature in a saltwater aquarium. In warm climates, a heater may not be necessary to keep a warm water aquarium heated but it is a good way to regulate fluctuations in temperature. Water chillers are generally only needed for cold water marine tanks and for aquariums being kept in very warm climates. To maintain water temperature, set your heater or chiller to automatically keep the water within the ideal temperature range and use an in-tank thermometer to double check.

Maintaining a saltwater aquarium is not an easy task. In addition to monitoring and making adjustments to pH and salinity levels, you must always keep your eye on the aquarium temperature. The temperature of a marine aquarium is very important to keep stable because even minor fluctuations can stress your fish or cause them to become ill - other tank inhabitants like coral may even die as a result of temperature change. Monitor your tank temperature closely and enlist the help of an aquarium heater or chiller to keep the temperature within the ideal range.

As long as you take the time to set up your aquarium properly in the first place, and perform all of the required maintenance tasks, you should have no trouble with your marine tank. Just keep in mind that tank temperature is related to nearly all of the other elements in your tank – it can have an effect on the health of your fish as well as the water parameters. To ensure the health of your fish and other tank inhabitants, take the time to determine the ideal temperature and then do whatever is necessary to achieve it.