Pouring chemicals into a goldfish bowl

Embarking on the journey of setting up your first aquarium is an exciting endeavor, but like any new hobby, it comes with a learning curve. In this blog post, we'll delve into some of the most common mistakes made by new aquarists and offer insights on how to navigate these challenges and ensure a thriving aquarium right from the start.


Mistake #1: Not Cycling the Tank

Perhaps the most common mistake new aquarists make is adding fish to an uncycled tank. Contrary to what any pet store employee might tell you, you cannot set up a new aquarium and add living creatures to it on the same day. Cycling is the process of establishing beneficial bacteria in the aquarium that break down harmful ammonia and nitrite. Without these beneficial bacteria, toxic waste compounds will accumulate, which can seriously harm and even kill your livestock. Some beginners may not fully understand or skip this crucial step due to impatience or misinformation, leading to harmful water conditions for the fish. Cycling takes time, usually several weeks, but it sets you up for success and saves you money and heartache by ensuring the safety of your livestock. Luckily cycling isn't a difficult process-- it only requires some bacteria starter, an ammonia source, and a bit of patience! Test kits are also useful to help you track the progress of your cycle so that you know when your tank is ready for its new inhabitants.


Mistake #2: Overstocking the Aquarium

New aquarists may be tempted to add too many fish to their tank too quickly. Overstocking can lead to poor water quality, stress for the fish, and increased susceptibility to diseases; so it's crucial to have the proper sized aquarium for the livestock you wish to keep. If you’re not sure how many fish a tank can safely house, you can get a rough estimate by using the inch-per-gallon rule as a guideline: approximately one inch of fish per gallon of water. Be sure to consider the fullgrown size of the fish when using this formula, and whether or not it needs to be kept in groups for optimal health. Also keep in mind that long, horizontal aquarium models may have more wiggle room (pun intended) than tall, vertical tanks due to the additional swimming space. Other factors affecting stocking potential include your filtration system, adequate aeration, and species-specific requirements. Remember that adding all your livestock at once is bound to spike toxic ammonia and nitrate levels, so try to add just a few at a time to give your tank’s beneficial bacteria colony time to adapt. 


Mistake #3: Inadequate Filtration

Choosing an insufficient or inappropriate filter for the size and type of aquarium is a common mistake. Proper filtration is essential for maintaining water quality and the overall health of the fish. There are several types of filtration systems available, and the choice depends on factors such as tank size, the type of livestock you plan to keep, and the level of maintenance you're willing to undertake.


Shop Sponge Filters

Best for Small Tanks & Breeding

If you’re looking for something simple, fry-safe or shrimp-safe, and don’t plan on having a large tank or high bioload, then you may consider a sponge filter. Sponge filters are easy to set up, affordable, require very little maintenance, won’t suck up any baby fish or shrimplets, and do not produce a strong flow, which can be desirable for certain fish and plant species. Sponge filters are generally best for smaller tanks, possibly up to 40 gallons with the right bioload or when running multiple, and they offer a means of physical and biological filtration. There may be times where you’d like to employ chemical filtration to get crystal clear water, reduce odors or discoloration, or remove recent treatments from the water column. In such cases a power filter or canister filter would serve you better.


Shop Power Filters

Best for General Purpose

Power filters are most commonly mounted to the back or side of your aquarium, although sometimes they are internal and mounted inside the aquarium itself. They contain a compartment to house premade filter cartridges, often with additional room to add other media of your choice. They are popular amongst many hobbyists because they are straightforward to install, accommodate the majority of tank sizes, and provide some degree of flexibility and customization in filtration capacity… all at an affordable price! Potential drawbacks would be noise from the externally-housed pump impeller, as well as being visually unappealing to some aquarists.


Shop Canister Filters

Best for High Bioloads, Large Tanks, & High Visual-Appeal Aquascapes

Canister filters free up space within and behind your aquarium by sitting in a cabinet beneath the main system, but their tubing, inlets & outlets will be visible in and around the tank. Their compartments are larger than most hang-on-back power filters, so you can easily increase their filtration capacity by customizing your filter media to suit your needs. Out of the three, canister filters are usually the most expensive, but they will often have higher filtration capacity and require less frequent maintenance. Both power filters and canister filters are great for water flow and surface agitation, providing much needed oxygenation to your tank inhabitants.


*Note: Some social media posts or product advertisements may lead you to believe that simply adding a few live plants will provide enough filtration for your tank. Although live plants do provide some level of biological filtration and nutrient absorption, they are not a substitute for a proper filtration system. Filterless planted aquariums are possible (check out the Walstad Method if you’re interested!); however, they require A LOT of plants and a relatively small bioload to be successful.


Mistake #4: Incorrect Water Changes

Regular water changes are vital for removing accumulated toxins and maintaining good water quality. Some beginners may not realize the importance of water changes or may neglect them, leading to deteriorating water conditions. Another factor to consider is how much water you change in one sitting. Since many fish can be sensitive to sudden changes in water chemistry, it's generally not recommended to change more than 40% of the total water volume at a time, unless you are addressing an emergency situation. The frequency of water changes will depend on your tank’s size and bioload: small tanks may need smaller but more frequent water changes, such as 10-20% weekly, whereas larger tanks may benefit from 30-40% changes on a biweekly or monthly basis.

It’s important to remember that removal and cleaning of aquarium hardscape & equipment is not necessary and may even damage your aquarium’s beneficial bacterial colony. Aquarium filter media bags can simply be shaken in dechlorinated water to loosen any debris and detritus. It is not recommended to run the filter media under tap water, as many water sources include disinfectants that can kill the good bacteria living in your filter. Don’t forget to always treat your tap water with a dechlorinating water conditioner before adding it to your aquarium!


Mistake #5: Choosing the Wrong Fish

Selecting fish without researching their specific needs, compatibility, and adult size can lead to problems. Some fish may outgrow the tank, become aggressive, or have dietary requirements that are challenging to meet. Here are just a few examples of common mistakes:


Housing goldfish, oscars, or plecos in tanks that are much too small for their adult size

We’ve probably all seen goldfish in bowls at some point in our lives-- whether in a movie, as a prize at the fair, or even as decor in offices or on wedding tables (yikes!). Although these species may appear small when young, they can all actually grow to be quite large and produce a lot of waste. Similarly, oscars and plecos can easily grow to over 12” and will require housing well over the 50 gallon range for optimal health, so if you’re looking to stock a small to medium size aquarium, steer clear of these species. 


Housing aggressive or territorial fish with incompatible tankmates

Fish like bettas, tiger barbs, some gouramis, african cichlids and oscars need to have carefully-selected tankmates when building a community aquarium. Bettas, for example, will not do well with other brightly colored and long-finned tankmates (they are named Siamese Fighting Fish for a reason!), and African cichlids prefer to be with their own species. Be sure to research your desired species carefully to ensure compatibility prior to adding to your community tank.


Housing an improper number or ratio of fish

Some species are more social by nature and prefer to swim in a pack. Common examples include tetras, rasboras, danios, and barbs. For these species, it’s generally recommended to keep a group of at least 6 to reduce stress and tpromote overall well-being. Other species may have recommended gender ratios, such as guppies, where you should maintain a ratio of 2-3 females for every male to reduce aggression and bullying. 


The bottom line is that you should research the species you intend to keep before bringing it home. Lack of planning in this department can easily lead to fish stress, disease, injuries, and even death, so please do your due diligence and avoid impulse buys at your local pet or fish store.


Mistake #6: Overfeeding

Overfeeding is a common mistake that can lead to excess waste, poor water quality, and health issues for the fish. Be sure to feed small amounts of high-quality fish food on a set schedule, and stick around to monitor your fish during and after mealtime. If they quickly consume all the food within a few minutes, you are likely providing an appropriate amount. If uneaten food remains after several minutes, then you are likely overfeeding. Be sure to remove any uneaten food with a net or siphon so that it doesn’t decompose and affect water quality. You may find it helpful to use clips, rings, or other feeding tools to concentrate the food to one single area for easier monitoring and removal. Some individuals choose to rely on automatic feeders to regulate the quantity and frequency of feedings-- just be sure to adjust the feeding gate and test it prior to first use. If you find that too much food is being released at the smallest gate setting, you can use a bit of tape to make the opening even narrower and keep the gate from shifting during operation. Also remember that with aquarium feeding, less is usually best. 


Mistake #7: Not Monitoring Water Parameters

Regular testing of water parameters such as pH, ammonia, nitrite, and nitrate is crucial. Failing to monitor these levels can result in unnoticed problems and stress for the fish. Generally speaking, testing should be done on a weekly or biweekly basis. In certain circumstances– such as when starting a new aquarium, adding anything new (plants, livestock, decorations, etc.), or keeping tanks with high bioloads– you’ll want to test more frequently. Any death, illness or unusual behavior in your tank should also warrant immediate testing to help diagnose and correct the issue quickly.


Mistake #8: Quick Changes to Water Condtions

Sudden changes in temperature, pH, or other water parameters can stress fish and lead to health issues. For this reason, it's essential to make any adjustments to the aquarium environment gradually. When performing a water change, try to match the water parameters such as temperature and pH as closely as possible to avoid drastic swings. Some livestock are more sensitive to sudden changes than others. For example, freshwater shrimp have a delicate osmoregulation process of balancing water and salts within their bodies. A rapid change in water parameters can create osmotic stress on the shrimp and interfere with their molting process, causing issues that often result in death. If you are keeping shrimp and notice that you lose a few every time you do a water change, consider dripping in the replacement water slowly over a gradual period of time to allow for proper acclimation.

Temperature control also falls into this category. Oftentimes new aquarists may consider heaters or fans to be unnecessary, often thinking that if the wildlife in the oceans & lakes can survive without them, then their aquarium fish will be fine as well. The issue is that our aquariums are much smaller bodies of water that can heat up and cool down much quicker than oceans, rivers, and lakes. A ten degree temperature swing could take weeks to months in the ocean, but may happen in mere minutes within your home. For this reason, it's highly recommended to closely monitor your water temperature with a thermometer or a temperature controller that can trigger a heater or fan to turn on automatically to keep your tank’s temperature steady and within a preset range.


Mistake #9: Skipping Quarantine

Bringing home a new fish is exciting, and it’s hard to resist the urge to immediately place it in your tank for all to enjoy. However, introducing new fish without quarantining first can bring in diseases or parasites to your aquarium. If you want to prevent the spread of illness, it’s best to practice patience and err on the side of caution by placing your new fish in a separate bare-bottom tank where you can monitor for a few weeks and treat if necessary. Even when starting up a new system, quarantining your livestock is important to avoid contaminating equipment and hardscape with difficult-to-eradicate diseases such as Ich, Columnaris, and Pseudomonas. It’s important to keep in mind that live plants can also be carriers of an array of diseases and unwanted hitchhikers such as pest snails and algae, so be sure to properly inspect and quarantine your plants as well!


Mistake #10: Acting on Impulse

Many beginner aquarist mistakes boil down to one simple thing: lack of research. To avoid these mistakes and countless others, new aquarists should invest time in learning about the specific needs of the fish they want to keep, proper aquarium maintenance, and the importance of patience in the hobby. Seeking advice from experienced aquarists and doing thorough research can contribute to a more successful and enjoyable aquarium experience.

If you’ve read this far, then you’re already off to a great start! Check the Learning Center for new articles, follow us on Facebook, Instagram, YouTube, and TikTok, or sign up for our newsletter to stay connected with the BRS Fresh community.