Are Tropical Fish Saltwater Or Freshwater?

Tropical fish come in freshwater and saltwater varieties. Learn more about the different types of tropical freshwater fish and tropical saltwater fish.

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Cardinal tetra
Cardinal tetras are tropical freshwater fish native to South America. charnsitr/Shutterstock

When we say a fish is tropical, this just means that it hails from tropical climes and that it will require warm water to thrive. Technically, when we call anything “tropical” from plants to birds to fish, this indicates that it is indigenous to the warm, humid, equatorial regions between the Tropic of Cancer and the Tropic of Capricorn, so quite literally between the tropics.

Tropical Fish Come In Freshwater And Saltwater Varieties

That being said, there are tropical freshwater fish and tropical saltwater fish, and less commonly, tropical brackish fish. Brackish fish typically come from estuaries and live in water that is slightly salty. Because of the intermediate and fluctuating salt content of the water they inhabit, they are generally not considered to be the best choices for those new to the aquarium hobby, but they are some fascinating fish nonetheless that we can cover in a future article.

The vast majority of fish available in any store are going to fall into the tropical category. Tropical fish will almost certainly require a heater in their tank to keep the water sufficiently warm to replicate their natural habitat (about 72 to 80 degrees Fahrenheit, depending on the fish). This is usually still far easier and much cheaper than needing a chiller to maintain temperate or colder water fish species.

It is often assumed that it is easier to keep freshwater fish compared to saltwater ones, but that is not inherently the case. It is true that since freshwater ecosystems don’t require the addition of salt in order to make the water the right salinity, there are less steps in the setup process and a lower margin for error when mixing water, but this does not necessarily mean that your first aquarium should be freshwater. It all depends on the fish you choose. So let’s take a look at some popular tropical fish that fall into either the freshwater or saltwater categories.

Types Of Freshwater Tropical Fish

Some of the hardiest and most robust tropical freshwater fish out there are guppies, mollies, platies, danios, cory catfish, and quite a few species of tetras. They are all relatively peaceful when kept in community aquariums and fairly generic in their feeding and housing requirements. Flake food is enough for their basic nutrition, but they certainly benefit from supplemental feedings of bloodworms, brine shrimp and Daphnia.

Zebra danio

Zebra danios are popular tropical freshwater fish. XEG/Shutterstock

Groups of tetras can make for stunning schools in community tanks and often wind up being the focal point of an aquarium because of the way they utilize every inch of space in the water column. The bigger the school the more comfortable they are.

Cory cats also do wonderfully in groups and spend most of their time scouring the bottom for bits of food. There are dwarf species that stay extremely small and others that can be several inches in length as adults, so it’s important to get the right variety for your tank size.

Guppies breed extremely readily, so if you do not want babies everywhere, keep either all males or all females. The males have much more elaborate fins and brighter colors so are usually the more popular choice.

Mollies and platies are both hardy and docile and are available in a wide variety of colors as a result of selective breeding.

Danios are active and engaging to watch, and in my opinion, one of the most attractive tropical fish available is the Zebra Danio.

Bettas, originally known as Siamese Fighting Fish, are absolutely gorgeous animals. They’re extremely aggressive with one another and need to be kept alone or with other non-aggressive fish. If kept alone, it is important to remember that although they can survive in small bowls, they will live much longer and be far happier in a larger aquarium. 

Types Of Saltwater Tropical Fish

Now on to tropical saltwater fish. Likely one of the first fish that comes to mind is the clownfish, or anemonefish, and for good reason. They are essentially the perfect aquarium inhabitants because even in the wild, they live within tiny territories and rarely venture more than a few feet from their host anemone. This in not the case with all clownfish species since some can get quite large and aggressive (e.g. maroon clownfish), but ocellaris and percula clowns are great options.

Percula clownfish, seen here in a carpet anemone, are popular tropical saltwater fish. Photo courtesy of Alexandra Rose

Damselfish are one of the hardiest fish out there and also quite beautiful, but unfortunately they tend to be aggressive. If you do buy a damselfish, it is best to choose a small species and make it the last addition to your tank. They ruthlessly defend their territories and are more subdued if all the other fish have had a chance to settle in and get comfortable first.

Many species of blennies and gobies are great for a range of aquarium sizes, but since some can get rather large, it is always advisable to find out the details of their adult sizes prior to buying them.

Chromis are beautiful and docile, and unlike most species in the damselfish family, are perfect in community tanks. A school of them can be a spectacular addition to a peaceful marine system. Some species of wrasses are good options as well.

Tropical fish tanks are extremely rewarding whether you decide to go with a freshwater or saltwater system. They both have their pros and cons, but at the end of the day, they are both windows into amazing aquatic habitats around the world. Do some research, decide which option is better for your particular purposes, and take pleasure in creating an ecosystem that will be enjoyed by both you and your fish.

Article Categories:
Fish · Freshwater Fish · Lifestyle · Saltwater Fish