Maintaining a tropical aquarium is not always easy. There are so many different factors to keep in check, from the temperature and salinity of the water, to the balance of algae to fish. As such, if you are first getting started with a tropical aquarium, it is important to choose fish that can tolerate some fluctuations. Here are four such species of fish that tend to be good choices for beginners.

Mollies

Mollies are medium-sized, black fish with some white spots. They are easy to find in fish stores, and they adjust to a new tank quickly. Mollies are pretty hardy. While they prefer alkaline water, they'll be okay if your alkalinity fluctuates a bit and takes a while for you to stabilize. Mollies are also pretty tame, so you don't have to worry about them cannibalizing your other fish.

Swordtails

These bright, orange fish are really fun to have in your tank. They dart about and interact with each other regularly, which can be fun to watch. Swordtails are inexpensive, which is another reason why they're good for beginners. They'll tolerate changes in the water, and they'll eat almost anything, from brine shrimp, to veggie flakes, to bloodworms.

Plecostomus

If you want a larger fish in your tropical aquarium, then a plecostomus is a great choice. This is a larger species of catfish. They're black in color with gray-white spots and predominant fins. Plecostomus spend a lot of time meandering around the bottom of the tank, which makes them fun to watch. They're very long-lived, docile, and tolerant of other species in the tank. However, because of their large size, they are only recommended for large aquariums.

Oscars

Oscars are sometimes known as tiger cichlids. They're grayish brown in color with blotches of orange and yellow. These fish are inexpensive and easy to keep alive. They will often follow your finger if you drag it gently over the outside of the aquarium. Oscars can be a little aggressive if left alone, so you will want to invest in a pair of them. They grow quickly, so make sure you have them in a big tank.

If you're just getting started with your salt water aquarium, any of these fish would be good choices. Talk to an employee at your local fish store for more information about tropical aquarium fish. They may have some other fish on-hand that are tolerant of changing conditions and that are ideal for beginners.