Multiple Betta fish

January 5, 2021
The 5-way Betta Aquarium with

[blue betta fish with orange background]Though “fish” is not the first animal you may think of when you hear the word “pet, ” the number of people keeping fish as pets is growing. According to the 2015-2016 National Pet Owners Survey, conducted by the American Pet Products Association, there are more than 95 million freshwater fish—with common goldfish by far the most popular species—and 9 million saltwater fish kept as pets in the United States.

Naturally, there are also veterinarians who specialize in fish health. One is Dr. Caryn Poll, a senior staff veterinarian at the and an adjunct professor at the University of Illinois College of Veterinary Medicine in Urbana. She recently offered advice on pet fish health and husbandry for newcomers to the hobby.

Selecting Healthy Pet Fish

According to Dr. Poll, species that are good for beginning freshwater fish owners include common goldfish, plecostomus, tetras, and betta fish.

“Keep in mind that betta fish are aggressive to other members of their species, ” says Dr. Poll, “so multiple betta fish, especially males, should not be housed together.”

Dr. Poll recommends acquiring your new pets from a reputable source, whether it be a pet store or fish supplier.

“Signs that a fish is healthy include swimming horizontally in the water column, a nice regular respiration rate, good coloration and appetite, fins that are in good condition, and an overall appearance of being comfortable, ” says Dr. Poll.

Tank and Water Quality

The tank should be large enough so the fish can swim around freely when fully grown, not just at the size when you acquire them. The common goldfish can grow up to 8 inches in length and, if cared for properly, can have lifespans of up to 20 years.

A fish tank should not be too close to a window, air conditioner, or heater because those will make it difficult to regulate the temperature of the water. Also, having a tank in direct sunlight will increase the rate of algal growth.

Water quality is fundamental to the health of the animals that live in the tank, so it is very important to follow recommendations carefully. For instance, you cannot put tap water directly into the tank, because tap water contains chlorine and other compounds that can be harmful to fish and other aquatic animals. Dr. Poll suggests “conditioning” tap water by letting it sit for a few days in a bucket to allow the harmful compounds to dissipate before putting the water into the tank. Another approach is to use de-chlorinators, which can be purchased at most pet stores, to make tap water safe to use immediately.

Partial water changes of between 10 percent and 15 percent can be done weekly or on an as-needed basis. “It is important to keep the water clean but not sterile, ” explains Dr. Poll. “Good bacteria live in the tank and help maintain a healthy environment. Over-cleaning or changing the water too frequently can disrupt this balance.”

Appropriate filtration is an important part of maintaining a healthy fish tank. Filters help circulate the water while removing debris as well as creating surfaces for good bacteria. Submergible heaters and lighting can be important for setup depending on the type of fish as well as plant species. The common goldfish does well in room temperature water.

Dr. Poll says it is a good idea to test the water in the tank using at-home test kits which can be purchased online or from a pet store. Parameters such as pH, temperature, salinity, nitrates, ammonia, and so on are important factors in maintaining fish health. Tanks that have been recently set up need more frequent water testing (and potentially more frequent water changes) until the bacteria can establish a healthy cycle. While it is always important not to overcrowd or overfeed a tank, with a new tank it’s especially important not to have too many fish at the same time to allow the tank to adjust between additions.

Care and Feeding

When deciding on tank décor, make sure to provide your fish with a place to hide. Plants, live or plastic, can be a nice addition. Live plants should be purchased from a reputable source, since these can spread disease and unwanted creatures, such as snails. Live plants help keep the water clean, although water changes will still be necessary.

Bringing new fish into an established tank may also introduce disease. Dr. Poll recommends quarantining new fish for a few weeks in a separate tank before adding them to the main tank to lessen that risk.

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