15 Mistakes First Time Aquarium Owners Make


Everyone has to start somewhere when starting a new hobby and freshwater aquariums are no different. It’s easy to get caught up in the excitement of owning a new fish tank and forget some essential steps. Read on for more information about the top 15 mistakes that new fishkeeps make with their freshwater tanks.

  1. Not Cycling the Tank

One of the absolute, number one mistakes that first-time aquarium owners make is not to cycle their tank. Ensure that your tank goes through the nitrogen cycle before adding fish or invertebrates to decrease the likelihood of death when introducing them to their new home. There are several ways to cycle your tank. The safest way is to set everything up and let it run unoccupied for several weeks.

I like having a planted tank because when the plants start to show new growth, it is a clear sign that the nitrogen cycle has completed, and it is safe to add fish. There are some ways to speed up the process if you just can’t stand looking at an empty tank for weeks. Check out our guide on how to properly cycle an aquarium.

  1. Buying Supplies and Fish at the Same Time

Right up there with not cycling your tank is buying your fish and supplies at the same time. If you do, you won’t have anywhere to keep your fish in the days to weeks it will take for your tank to cycle. It might seem like common sense to get everything in one trip, but this can be a way to gain knowledge as you go and add excitement to the learning process.

You can buy a few things, take them home, and add them to the tank, then repeat the process. This can be especially fun with children as they will have more trips to look forward to. Once everything is set up correctly, cycled, and you’re ready to go, it’s perfectly fine to add new inhabitants or more decorations if you find you’re missing anything – just don’t go overboard!

Make sure you have the space and knowledge you need for any new purchase.

  1. Inadequate Species Knowledge

You absolutely must know everything there is to know about the freshwater fish you intend to keep. A species only tank is easiest, as there’s only one animal you need to worry about, but most first-time aquarists want to have several different kinds of fish. The great thing about freshwater fish is that there are so many that can be kept together. Make sure you do your research! There are several species that like the same temperatures, acidity, and water movement.

With so many fish, there is sure to be a comfortable middle ground that will suit any number of animals.

  1. Trusting Retail Pet Store Employees

It might seem like common sense to trust the people selling you fish to know what they’re talking about. Unfortunately, this is usually not the case. Retail pet store employees often lack specialized knowledge of the animals they are selling. This shouldn’t be a negative judgment of them. Between juggling hamsters, lizards, fish, cats, and birds, they have their work cut out for them! This being said, retail store employees aren’t experts.

They aren’t paid to be. And while they may have the knowledge to help first-time aquarium owners on their fishkeeping journey, the time commitment needed for this hobby doesn’t provide profits for their employers. While that’s perfectly fine in the business world, it doesn’t make for great advice when it comes to providing a good life for your animals. 

  1. Overstocking

It’s so tempting to fill your tank with lots of life and activity. This is perfectly fine, but be sure to make allowances for growth. A tiny goldfish, less than an inch in length when purchased, can grow up to a foot long! Make sure to research your chosen species properly to see how big they’ll get before adding them to their new home. The golden rule for aquariums is one inch of full-grown fish per gallon in your aquarium.

So, while many fish are quite small when purchased, they can grow quite large and quite rapidly. Make sure to know the full-grown length of your fish before you add them to the tank to avoid overstocking. It might look a bit bare when starting out, but be sure that they will fill out with time. 

  1. Overfeeding

Freshwater fish are voracious feeders. If you let them eat all they want, you’ll see them balloon up quickly. Some fish will even eat so much their insides rupture, causing death. A good rule of thumb is to let your aquarium inhabitants eat all they can within five minutes. Then, remove any left-over food from the tank. This can be particularly difficult for young fish because they need to be fed several times per day.

As they age, the number of feedings should be decreased. Keep a close eye on your new fish to see how much they can eat in a few minutes, then adjust feeding amounts accordingly. 

  1. Not Keeping a Maintenance Schedule

Fish tanks should never be too clean or too dirty. This is a delicate balance. Test your water every day when you first have an aquarium. This will give you an idea as to how the water parameters change. Then, you can get a good idea as to when you should do water changes to keep your fish happiest. It will take a few weeks to get the hang of things, and there is no one-size-fits-all approach.

While it will take a little to get everything down, you’ll soon know about how often you should do maintenance on your tank and can plan accordingly.

  1. Improper Decorations

Different fish like different kinds of homes. Some like coarse gravel in dark colors, while others must have dense plant growth and sand to be happiest. Looking into an animals’ natural environment is a great way to know what kind of situation with which they will be most comfortable. If an animal naturally hails from slow-moving rivers, use sand as substrate with decorations that approximate river rocks, downed tree roots, and boulders.

If your fish come from pristine, high flowing waters, make sure you have a proper filter pump and do regular water changes. While most freshwater aquarium fish are relatively adaptable, all will do best if they have a comfortable home. Additionally, there are some types of decorations that can be harmful to delicate scales, such as sharp edges on plastic items or gravel that is too rough.

  1. Impulse Buys

Getting a new aquarium is very exciting. There are so many things to plan for and buy, it can be easy to start making purchases without proper planning. While it’s fine to buy something on impulse here and there, it should be kept to small things, like a new decoration, piece of driftwood or a plant you know will survive in your tank. It’s best to have a set plan before you make any purchases at all.

I like to have a document listing aquarium animals, plants, decorations, and themes that I would like to explore one day. Then, when I have the time and funds to dedicate to a new aquarium, research the animals and what they need to be happiest. Finally, I start a ‘wishlist’ on Amazon or an online aquarium retailer with all the things I will need to plan for expenses. 

  1. Just Getting a “Small Aquarium”

It may seem like getting a small aquarium would be easier for a beginner. However, this is often not the case. Because small aquariums hold so little water, they are prone to sudden fluctuations in parameters. Just one little thing going wrong can spell disaster. A first time aquarist might be alright with something like a five-gallon tank to keep a single fish, such as a Betta, but it’s better to start with something like a twenty or forty-gallon. This way, you are more likely to encounter stable water conditions. 

Additionally, it gives you more space for your fish. Lots of first time fishkeepers like to start off with a community tank with several kinds of fish. With a larger tank, you can keep more fish.

  1. Keeping Fish in a Bowl

Never, and I repeat, never, keep an animal in a bowl unless it’s an absolute necessity. The common trope of a goldfish won at the carnival is so ingrained that it might seem proper, but it isn’t. Anything that has gills to breathe will need a water pump, or at least a bubbler to keep the water aerated and moving (and this only for a short time if its the only source of movement).

Fish are extremely unhappy when they aren’t kept in an environment that suits them and will quickly die. Make sure to do your research for any new fish you acquire!

  1. Self-Cleaning Aquariums

As alluring as a self-cleaning aquarium is, it doesn’t exist. There may be certain set-ups and particular aquarium animals that require less maintenance than others, they will need attention from time to time. The ideas of “eco-spheres” have become popular in recent years, a type of aquarium that produces its own food and oxygen with animals that clean the container, but this type of set-up should never be attempted for a first time aquarium owner.

Another popular “self-contained” option is a vase with a water plant and Betta fish. These poor Bettas will live for a little while, but a single plant isn’t adequate food for them, and they still need a proper pump, filter, and heater to live a long, healthy life.

  1. Cleaning out the Entire Tank

As stated above, aquariums should never really be too dirty or too clean. When you empty the tank and clean every part, you will kill many bacteria and tiny organisms that are actually beneficial to the health of your freshwater inhabitants. Additionally, the nitrogen cycle will be destroyed, so you’ll have to cycle your tank again for weeks before it’s safe to replace your fish.

There is so much advice online that talks about cleaning your tank and tank maintenance; it can be easy to think you must clean the entire thing. But, a regular schedule that includes substrate vacuuming and removing excess algae from the tank walls and decorations is usually all that is required to keep everything in top shape. The only time you should clean the entire tank is if there is a major problem, like tank failure, or if you want a clean slate to start a new set-up.

  1. Not Having an Emergency Plan

What will you do if your power goes out? What if you have to take an unexpected, extended trip? If one of your fish gets sick, what do you do? These are just a few of the emergencies that can come up for all fish keepers. What separates successful from unsuccessful aquarists is having emergency plans for when something goes wrong. I live in an area that is prone to power outages due to hurricanes and tropical storms.

So, I always have a supply of batteries for my backup emergency pumps and aerators. It’s also a good idea to have a person you trust knowledgeable on basic fish care in case you need to go out of town. I have friends who know how to feed my fish. So, in case of an emergency, they can care for them while I’m gone. Try to think of anything that might go wrong that would keep you from caring for your fish and plan appropriately.

  1. Constantly redecorating your tank

Once your animals are safe and happy in their environment, let it be. Many animals have their own territories or spaces they feel comfortable in the tank and will be out of sorts if you rearrange things too frequently. There’s nothing wrong with moving things around every once in a while. But, keep your inner interior decorator at bay.


Every single expert aquarium owner has started exactly where you are now – as a beginner! The only way to get experience is to practice, so good luck! Our Start Here section has some great advice for novice fish keepers.

Be the first to comment

Leave a Reply

Your email address will not be published.