Many new fish keepers find more myths than facts about how to keep their pets happy and healthy. Here are some tips to become a better fish keeper.

Fanciful image of goldfish in a lightbulb
Get inspired to be a better fish keeper!
Photo by Esteban Bernal on Unsplash

It’s never a good idea to go into a new venture blind, so why do that with an animal? Fish are pets, not toys, not decoration, not just a hobby. All pets have needs to consider to give them the best lives possible. The same basic rules of pet ownership apply to fish just as they would a cat, dog, rabbit, bird, lizard, or any other domestic animal. Know what you’re getting into and be willing to make changes. These are some of the most common beginner mistakes of fish keeping.

Have the Proper Equipment

Nano tank with live plants
Checklist: tank, heater, filter, decorate!
Photo by Huy Phan on Unsplash

The goldfish in a bowl is as common a cliche as rabbits eating carrots. Both are dangerously incorrect misconceptions. You shouldn’t keep fish in a bowl for the same reason you wouldn’t raise a child in a closet. They may seem okay, but what’s going on here is abuse and their well-being will suffer for it. A common myth is that a goldfish will grow to the size of its bowl, but this not true. While the fish stay the same size, their organs continue to grow. Goldfish only live up to 2-3 years in a bowl before they die from organ failure due to constriction. In a proper-sized tank or pond, goldfish can live for decades and grow to over a foot long. The recommended tank size for a single goldfish is 20 gallons. Tanks allow more room for your fish to explore. Different fish have different needs, so research is key. Avoid tanks under 5 gallons, as it is difficult to maintain the nitrogen cycle (more on that later).

Another disadvantage to small tanks and bowls is a lack of room for proper equipment. The most common fish you see in the pet store are tropical or subtropical, meaning they need heated water. Your local pet store carries a wide variety of heaters for tanks of all sizes. Another necessity omitted from fishbowls is a filter. Filters cycle your fish’s water through layers of carbon and biological media. This cleans and oxygenates the water, reducing the need for daily water changes. Filters come in many styles, but the Hang-on-back or HOB filter is most common. These are also available at any pet store.

This is a good start, but there are still more pieces of equipment to consider depending on the fish you want. Consider getting air stones, thermometers, nets, and water test kits. These will also contribute to successful fish keeping. Fish can be easy pets, but not always cheap ones! The good news is this cost is all upfront. An established tank can run with minimal cost and effort for years of enjoyment.

Some Fish Need Friends

Black skirt tetra and a friend
Schooling fish swim in mesmerizing patterns.
Photo by Cofish Aquarium on in Unsplash

When the kids wanted a fish, they probably got just that, a single fish. While this allows for smaller tanks, many species of fish prefer to form schools or live in groups. Schooling is a defense mechanism performed by wild fish. Think of sharks and dolphins going after “bait balls” on the nature shows. Your pet fish don’t know that they are safe from predators in your home aquarium. Stressed, lonely fish may hide or even have a shortened lifespan.

Tetras are one of the most common schooling fish purchased as pets. There are many varieties of Tetra including Candy Cane, Black Skirt, Neon, and “Glo” tetras. All types prefer a school size of six individuals or more. Consider this when you go to buy a tank. Do you not only have enough space for the fish you want, but all his buddies as well? Fishkeepingworld.com recommends a 20-gallon tank for a school of 15 tetras.

Many popular fish are shoaling as opposed to schooling. This means they like the company but won’t swim in tight formations. This means you may keep fewer fish, but only if you’re building a single species tank. Guppies, zebra, danios, and catfish are some of the most common shoaling fish found in stores. Each prefers groups of at least three or more. This varies by species, so do your research! Like schooling fish, more is always merrier. Best practice: get the biggest tank you can afford. It is better to understock a big tank rather than overstock a small one.

Some Fish DON’T Need Friends…

Bettas are beautiful fish. It’s easy to understand why you would want the biggest tank to keep one of every color. Unfortunately, bettas are territorial. They will fight one another until one or both of them die from exhaustion. Despite common myths, females are also aggressive. It is sometimes possible to keep a group of female bettas (a sorority) together. There’s another article’s worth of information on how to keep a sorority, though.

Another common yet aggressive fish you may see in stores is the gourami. Gouramis are a close cousin of bettas. Males are aggressive, but only with their own kind. You can keep gouramis alone or in male-female pairs. There are many gourami types of various aggression levels. The dwarf honey gourami is one of few varieties considered to be peaceful. They even prefer small groups to shoal with. The tiny sparkling gourami is downright shy. Also, consider whether your fish is conditionally aggressive. Tiger Barbs are peaceful, but only in schools. A common fish keeping mistake is buying too few Barbs. This leaves them feeling insecure and aggressive toward other fish out of fear.

Keeping any aggressive fish with other species is possible, but risky. This is not the best idea for beginners. All varieties of betta and gourami are carnivorous and may hunt other fish or shrimp. Learn more about your own fish’s personality before risking their safety.

The Nitrogen Cycle

An important thing new fish keepers miss is the nitrogen cycle. Ever heard of new tank syndrome? In short, it means you can’t just keep a fish in any random cup of water and expect it to be okay. There are many important differences between the water you find in a lake and what comes out of your tap. The most important of which is the nitrogen cycle.

Fish expel waste from their gills while breathing. This waste breaks down and accumulates in the water as ammonia. This is highly toxic to your fish. The nitrogen cycle is a natural process in which beneficial bacteria break ammonia down into nitrate. Nitrate cannot break down any further and can still be harmful in high quantities. You can remove it with live plants and weekly water changes. Replace your tank water with spring water, well water, or dechlorinated tap water. Most people use tap water and buy dechlorinating products from their local pet store.

The easiest, yet slowest way to establish these good bacteria in your new tank is to add a bit of fish food and wait. Depending on the size of the tank, this could take weeks to over a month to complete. Buying a water testing kit at the pet store will be necessary for helping you know when your tank is ready for fish. For intermediate fish keepers, you can try a fish-in-cycle. This involves adding fish before the cycle is complete. This can be faster, but it involves a lot more work. It requires daily water testing and changes to combat ammonia spikes. Don’t try this with sensitive or expensive fish. Ammonia spikes can happen without warning, costing you the life of a rare or pricey fish.


To recap, here is your checklist of things you should know before buying a fish:

  • Recommended tank size for fully grown fish
  • Preferred range of water temperature
  • School size, if applicable
  • Compatible tank mates (if building a community)
  • Preferred foods – plants, proteins, sinking, floating, live, frozen, or pellet?
  • Do they need any extras? Airstone, hiding places, specific pH, or hardness.

If, after reading this, you realize that you’ve been treating your finned friend poorly, don’t fret! Many fish are resilient. They can bounce back with minimal effort after making these adjustments. If you find yourself with a species you cannot care for long term, there are ways of dealing with that. Many larger species of fish like the common goldfish take years to grow. Enjoy them while you can and consider re-homing them when they outgrow their tank. A good pet store has experience helping novice fish keepers with these and many other issues. They will often accept an over-grown fish in the interest of getting them to a better home.

These are some of the most basic tips and tricks to improve the quality of life of your fish. These changes can improve the color, temperament, and longevity of your pets. Allowing you to enjoy them for years! This is only the beginning, there’s a lot more to discover beneath the surface. The best information in fish keeping is that of experience. Let me know what you think and what has worked for you!