Pet Fish Guide: What You Need To Know

Written by A-Z Animals Staff
Updated: October 11, 2022


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For many people, their first pet was a fish. Indeed, it was probably a goldfish, kept by itself in a goldfish bowl. Often, these pet fish cost nothing as they were given out as prizes at carnivals and funfairs. But as they grew up, these goldfish owners learned a few things about pet fish. First, a goldfish bowl is really not the best place to keep a goldfish. Second, there are so many other kinds of pet fish out there that you could write volumes on them. To be healthy and happy, these fish need much more than a bowl full of tap water and a substrate of pretty glass beads. The purpose of this guide is to let you know just what you’ll need to be a good pet fish parent.

Before Buying A Fish

Buying a fish used to be simple as in the example mentioned above. But people have learned that fish have needs that are at least as complex as those of a cat or a dog. Indeed, depending on the fish, maintenance of your pet may be more involved than you thought. Breeding certain fish, such as bettas, adds another layer of complexity. Because of this, it’s important that you read up on the type of fish you want.

First, you need to buy your fish from a reliable seller. Ideally, you should go in person to the seller and check out the fish for sale. They should be vigorous, bright of eye and a good color. The breeder and/or the staff should be able to answer any question you have about the species of fish, its life cycle and its needs. When it comes to price some fish are inexpensive as are the common goldfish while others are eye-poppingly expensive. Of course, you won’t just be spending money on the fish but on the accouterments that go with it.

Another thing to consider before buying a fish is if you have enough room in your house or apartment for the size of tank you need. You may find that you have enough space, but the space doesn’t work because it is not near an electrical outlet or it’s in the way of something or it gets direct sunlight, and even light-loving fish shouldn’t be placed in direct sunlight.

You’ll also need to determine if you want a variety of fish or just one kind. If you want different kinds of fish you need to find out if they can live together. If you have your heart set on a certain species, you will need to know if that fish can even live with a member of its own species or a conspecific of the same sex. Guppy owners are told to maintain a ratio of two females to one male because too many males in a tank will fight each other. Researching fish sociability is a must.

You should know whether you are able to easily obtain the food the fish eats. Some cichlids, for example, are predators and will only go for live food. Other fish such as surgeonfish are largely herbivores.

A pet fish owner should also arrange for the fish’s care if they have to be away for a while. This may mean a diligent friend, neighbor or family member or a system that automatically feeds the fish, turns the lights on and off and adjusts the temperature.

How much does a pet fish cost?

The cost of a pet fish is wildly variable. A plain guppy might cost 10 cents, though a fancy show guppy can cost $60.00. On the other hand, the platinum Arowana can cost as much as $400,000. This exquisite fish also grows to nearly 5 feet long and needs a 250-gallon tank.

Assuming you’re not an oligarch, you’re probably not going to spring for a platinum Arowana. But another popular, pretty and affordable fish might be a betta, which used to be known as the Siamese Fighting Fish. Let’s say you don’t want to breed this fish, and you decide to buy a single beautiful, rainbow-colored male betta. He’ll set you back about $15 to $40. But even before that, you’ll need a 5 to 10-gallon tank, which costs about $30. (Here are the best betta fish tanks, reviewed and ranked.) The substrate can be gravel, stone or glass marbles, which can run to about $15.00. Plants, live or artificial and toys to keep the betta amused will cost about $40.00.

You’re also going to want to go for a filter. A best buy for a 10-gallon tank costs about $41. An aquarium heater runs an average of about $15, a lid or hood with an LED light might cost about $30.

Betta fish prefer live food but can also eat dried foods. You will want to get the best food you can afford. These include daphnias, mosquito wrigglers, fairy shrimp and bloodworms. A half an ounce jar of baby brine shrimp can cost about $14, and you can buy about 200 live daphnias for about $30.00. Frozen fish food from a local pet store is also available, and an 8-ounce container of frozen brine shrimp can go for about $10.00. You can also freeze live food yourself. Dried fish flakes made specifically for bettas can be had for about $5.49 for about a quarter of an ounce. Food is certainly your most ongoing cost when you adopt a pet fish. The rule of thumb says that a betta should be fed twice a day, and the amount of food should be no larger than its eyeball. Maybe you can assume that the food lasts about two weeks to a month. Let’s say your betta fish lives for about five years, even though some lucky ones have lived for as long as 10. So, upfront costs would be:

  • Fish: $15
  • Tank: $30
  • Substrate: $15
  • Plants and toys: $40
  • Food, live, dried and frozen: $59.49
  • Filter: $41
  • Air pump: $20
  • Heater: $15
  • Hood with light: $30

Upfront costs come to $265.49.

Since the food comes to about $59.49 per month, that will run you $3569.40 over the betta’s five-year lifespan. You might need to store medications such as Mercurochrome, antibiotics or aquarium salt. These medications may cost about $100 if they’re needed, or you might even have to take your fish to the vet. A trip to the vet may cost between $50 and $100 dollars just to get the fish checked out. If the vet does house-calls, the price can rise from $200 to $300. You may need to replace a live plant or two, which might cost about $15 per plant. So, with the upfront costs excluded, the cost of owning a betta comes out to as much as $4084.40 over the span of its life.

New Owner Shopping List: What To Buy

The sheer amount of stuff you’ll need to buy to keep your fish happy and healthy is surprising. Indeed, you may need to buy more stuff for a fish than you would for a dog or a cat, for you basically need to recreate the “natural” habitat of an animal that lives in water. This is what you need to get even before you bring your fish home:

  • A tank that is the right size for your fish
  • A tank lid or hood with or without a light
  • A tank light if the lid doesn’t come with one
  • A spare tank to quarantine a sick fish
  • A thermometer
  • A heater
  • A filter
  • Substrate
  • Plants, real or artificial
  • Rocks
  • Pieces of wood
  • Places to hide such as a terra-cotta pot placed on its side or one of those ceramic hollow logs
  • Water
  • Salt mixture if you need saltwater for marine fish
  • Water and pH testing kit
  • Aerator, depending on the size of the tank
  • Hydrometer for marine aquarium
  • Fishnets
  • Forceps
  • Siphon
  • Bottle brushes
  • Pipe cleaners
  • Toys such as floating logs and moss balls
  • Food (Here are our top picks for best flake food for fish.)
  • Floating feeder
  • Magnetic tank cleaner
  • OPTIONAL: Aquarium cabinets are great for storage and presentation. Here are some great aquarium cabinet options.

Ongoing Needs: What You Need to Care For Your Fish

By the time you get your fish home, the aquarium should be ready for it. According to veterinarians, you should place the fish while still in the bag into the water in the aquarium instead of simply opening the bag and dumping the fish in. This lets the water in the bag reach the same temperature as the water in the tank. As this happens, you can add some of the tank water to the fish’s bag. This takes about an hour. Then, using a net, gently scoop up the fish and place it in the aquarium. Do not simply dump the fish out into the tank or pick it up with your hands. The water from the bag shouldn’t mix with the aquarium water. Here’s what to do during the first month home:

  • Check the water quality, the pH and the temperature every day. You may notice a high nitrite level after the third week. If you need to change the water, do it gradually. Don’t take your new fish out ad scrub down the tank.
  • See how much food the fish eats. You might want to underfeed it at first. Eventually, you’ll learn how much to feed your fish so that it’s neither underfed nor grows obese from overeating.
  • Watch out for illness. Sick fish have a dull color, may show white spots on their scales and “pant.” Don’t diagnose the fish, but call a fish veterinarian.
  • If all is well, the fish should be acclimated to the tank by the end of the month.

Exercise and Ongoing Care

One of the things that make fish such sought-after pets is that the great majority are really easy to take care of. They don’t need to be taken for walks, exercised or have their fur brushed or washed. They don’t need shots or regular trips to the vet as part of ordinary health care. What they do need are:


Over time you’ll find out just how much food your fish needs.

A Healthy Environment

Check the water regularly for bacteria and nitrate build-up. Make sure that the temperature and pH are where they need to be to keep the fish healthy. A rule of thumb is to partially change the water every two or three weeks and more often if you have a lot of fish in your tank. A full water change should be done very rarely, if at all.

Mental Stimulation

Yes, fish need mental stimulation as much as fur babies. This too is simple. Many fish can be fascinated for hours by ping pong balls or things that blow bubbles. Many fish, such as tetras, need companions. These can be members of their own species or members of species that won’t try to kill them or vice versa. Some fish such as the white-lined triggerfish are surprisingly responsive to their owners and want to interact with them as well.

Feeding Your Fish

Many pet fish are carnivores that prefer live food such as insects, brine shrimp, tubifex and other types of plankton. Some of these carnivores can even be fed bits of meat. Others are omnivorous and will eat live food, dried food and plant material. Carnivores tend to eat sporadically while omnivores and herbivores graze throughout the day, or if they’re nocturnal, throughout the night.

If you have a tank that has both carnivores and omnivores, it may be best to sprinkle in some food throughout the day to keep both of them happy without leaving any food in or on the water to befoul the tank. Some people utilize an automatic floating fish feeder, which can be programmed to dispense food at a certain time. Some fish owners feed their fish by hand. If you’re lucky enough to have a koi pond, hand-feeding is one of the pleasures of keeping these beautiful carp.

How Long Will Your Fish Live?

How long a fish lives depends on its species and the care it receives. Some life spans are:

  • Goldfish: 10 to 25 years
  • Dracula goby: Two to five years
  • Killifish: Two years
  • Clarion Angelfish: As much as 40 years
  • Convict: 10 to 20 years
  • Banjo catfish: Six to 12 years
  • Pearl danio: Five years
  • Oscar: 10 to 18 years
  • Clown loach: Over 15 years

Common Health Issues For Fish

Unfortunately aquarium fish are subject to a variety of health issues. Many can be prevented by making sure the fish has a healthy environment and a proper diet, but some seem to pop up out of nowhere. Among them are:

Ich or White Spots

Ich is short for Ichthyophthirius infection. It’s caused by a parasite and manifests as white spots all over the body that the fish tries to rub off on the sides of the tank.


This disorder with the old-fashioned name is caused by bacteria. It causes organ failure, bulging eyes and bloating. The fish stops eating and grows listless.

Swim Bladder Disease

This is another bacterial disease and can be caused by injuries or bad water quality. The fish has trouble swimming. It swims on its side or upside down and has a swollen abdomen.

Fin Rot

This disease is prevalent in fish with fancy fins, such as bettas. It starts at the tip of the fin and grows toward the body. Fortunately, this bacterial disease is easy to treat.

Fungal Infections

The fungus can grow on areas of the fish’s body that are no longer protected by the mucus coating. Fungal diseases are contagious, so your fish is going to need to be quarantined if it lives with other fish.

Where to buy your fish

Most aquarium fish are easy to find and can be bought at a pet store. Just make sure that the fish you’re looking for is active, alert, has strong coloration and has no sign of bloat or fungus, slime, pop-eyes or shredded fins. If you want more exotic fish, you may need to get in touch with a breeder who should be able to answer all of your questions with regards to its care.

You can also buy fish online, but that comes with some risks. It’s better to buy your fish in person, but you’ll have a greater variety of fish to choose from if they’re bought online. The retailer’s website should be extensive, and they should be able to answer your questions. You should get a guarantee that the fish will arrive alive and healthy and that you’ll be reimbursed if it doesn’t.

Special Considerations With Fish

People who seek to be fish pet parents should know that they are far more diverse than cats or even dogs. The biggest Great Dane and the tiniest chihuahua all belong to one species. There are about 28,000 species of fish and each have their own way of being in the world, from the tiny zebra danio to the huge and pricey platinum arowana. It’s up to the owner to provide the best environment and the proper diet for their fish.

About the Author

AZ Animals is a growing team of animals experts, researchers, farmers, conservationists, writers, editors, and -- of course -- pet owners who have come together to help you better understand the animal kingdom and how we interact.

Pet Fish Guide: What You Need To Know FAQs (Frequently Asked Questions) 

Can I take a fish out of the wild and keep it as a pet?

No. The fish may be endangered and should not be removed from the wild. Also, a wild fish just may not be able to adapt to captivity, even if you think you know how to take care of it.

Should I breed my fish?

Whether you should breed your fish depends, like everything else, on the species. Some species such as the Aenaeus grouper just don’t breed in captivity. Others, such as the blue panchax, breed easily. Still other fish need special handling when they reproduce, such as the betta. Others need plants to lay their eggs on or a special diet.

When should I do a full water change?

Most experts say that you should never do a full water change which means you take all of the water out of the tank, and replace it. This will change the ecology of your aquarium and may shock or even kill fish who are already traumatized from being removed from their tank.

Can I pet my fish?

You should not pet your fish. No fish should be handled with bare hands, because the mucus protects their scales, and it can come off on your skin. Not only this, but in some fish such as the six-lined grouper the mucus is poisonous. Other pet fish can bite or have venomous spines.

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