Common Fish Keeping Mistakes

22 Common Fish Keeping Mistakes

If you know them
they don’t kill your fish!

We have all been beginners in any hobby we pursued – fish keeping as well! – and making mistakes is natural and good. The bad thing with fish keeping mistakes is that you put the life of your livestock at risk.
To help you take care of your fish since the very beginning, we have identified the 22 most common fish keeping mistakes with the hope you can learn from our experience and fast track your learning curve,
Are you wondering why your fish are dying in your new aquarium? Are you worried that you are doing something wrong?

Setting up an aquarium and keeping everything alive and well inside the tank can be quite overwhelming and sometimes things don’t go as you planned.

Even with your best intentions and even if you followed your plan perfectly, mistakes happen.
Unfortunately, making mistakes in the aquarist’s world sometimes means fish loss.
Here is the list of common fish keeping mistakes new, and even veteran hobbyists sometimes make that may put their habitat in peril.
Let’s dive in!

Mistake No 1
Not Cycling Your Tank

This is one of the most common mistakes that new hobbyists make that can easily be avoided. It is the cause of many problems and should be taken seriously. When setting up a new tank, you may be tempted to throw everything in and make it look like your what you planned as soon as possible. Eagerness is one of the main problems of the new aquarist. Patience is needed in the beginning if you wish to have healthy habitable water for your fish to prosper in.

When we talk about cycling the tank, we mean letting the water break-in to make it liveable for your fish, and even for some of your plants.

Good bacteria need to form and grow inside the new tank in order to sustain life and keep water clean. These bacteria are essential to rid the aquarium water of toxins that are harmful to your fish. Toxins like ammonia and nitrate are broken down by the bacteria and water is naturally kept clean. This cycle may take anywhere between 3 to 6 weeks.
A common mistake to make when cycling your tank is to add ammonia neutralizing additions. This may sound like a good idea but it is, in fact, a very bad idea when cycling the tank in the beginning. The bacteria actually need ammonia to form and grow colonies. Without the presence of ammonia, the bacteria will take longer to flourish and your tank longer to cycle.
Liquid bacteria is available on the market and is an excellent option to add when cycling your tank for the first time. It will help in the overall cycle time significantly. It may actually mean 3 weeks instead of 6. You can buy this supplement in liquid or pulverized form from your fish store or online. It is recommended to add these bacteria in a new tank but never in an established tank as this may be catastrophic to the already stable water. There are many options, we have had good results with Api Stress Zyme solution that works for fresh and saltwater. Click here to see more about Api Stress Zyme solution on Amazon.
Here is an excellent article providing in depth information on how to cycle your aquarium.

If you wish to learn more about the cycling period, take a look at this fun and easy to read article explaining the nitrogen cycle.

Mistake No 2
Not Putting New Fish into Quarantine

It is so tempting to come home with your new fish and want to introduce them into your aquarium straight away. This is not the best thing to do as you may be introducing diseases into your healthy tank. If you have an established aquarium with cycled water and happy fish, you will want to keep it this way. The most common reasons for this is the cost, extra maintenance, and space needed for the extra tank. The good news is that it doesn’t have to be a huge tank at all, and it doesn’t have to be fully decorated as your main tank. If you have the space and can afford it, then by all means it is recommended you use this technique to keep your water levels good and your fish disease free.

When you bring new fish home form the fish store, they will naturally be a little stressed from the transport and may need some quiet time to adjust and calm down.

Throwing them into a tank full of new mates may make them more agitated and anxious. Stressed fish may not survive the initial introductions.
Another reason to quarantine the new fish is that they may be carrying diseases or even parasites from their previous tanks. You definitely don’t want to introduce damaging substances into your healthy water and experience dying fish.
Your fish should preferably be in quarantine from 2 to 4 weeks before introducing them into your aquarium in order take the time to treat them for any diseases they may possibly have and give them time to acclimatize.
Here is a great article explaining the quarantine tank. They explain how to set it up and care for it.

Mistake No 3
Not Checking the pH Level

One of the most important things in keeping water healthy is to keep a stable pH level. Your water and fish may seem fine, but if your pH levels spike you may start to have problems. The only way to determine if your pH level is accurate is to test it. It is easy to omit this step when your water looks ok and your fish don’t seem sick. Skipping this test is a common mistake to make when starting this new hobby.
A “regular” pH level varies from aquarium to aquarium. Your pH level will be determined by the fish and plants that you have in your tank. “Normal” usually means anything between 5.5. to 7.5. Anything outside of these numbers means that you have a high or low pH level. You will have obviously researched your fish and know the proper pH level to be kept in your tank. Most fish can live slightly outside of their recommended pH level. What you need to be careful are rapid spikes in levels.

A low pH level reading means that your water is acidic and a high pH reading means that your water is too alkaline.

Affordable and easy-to-use test kits are available on the market to test your water regularly. You will want to test your water weekly to make sure everything is under control and that the level remains stable.
Here is a quick read about how to naturally raise the pH level in your aquarium.

Mistake No 4
Under Cleaning

Starting a new aquarium and taking on the hobby of aquarium keeping requires work. You can’t be lazy when practicing this pastime. It requires regular daily, and certain weekly, chores that cannot be overlooked or omitted because you will rapidly start to go through fish loss.
The tank is a closed environment and even with the 3-step filter and other cleaning supplements you have installed, it absolutely requires regular partial water changes. At least 10-20% of the water needs to be replaced every week or so or when the test results show a problem. These are called partial water changes and require you to remove some water and replace it with fresh water.
The gravel needs to be vacuumed regularly, but not excessively. The filter cartridges also need to be rinsed and sometimes replaced in order to keep them working properly.

Mistake No 5
Over Cleaning

On the other spectrum, over cleaning can also be detrimental to your aquarium’s health. Bacteria need to grow colonies and are present to absorb some of the toxins in your tank. Over cleaning your gravel and filter media will rid your water of the precious good bacteria that is working in keeping your water clean. The slimy substance on your filter media should not be completely removed.
You may have the instinct to keep your aquarium super clean because it looks better and you may think that it’s best for your water quality, but this is a common error to make. You need to be aware of your water quality, but not get over consumed in keeping everything sparkly clean. Remember that the slimy stuff in your filter is there to help you.

Mistake No 6
Using Tap Water to Wash Your Filter

This may seem like the most normal thing to do. Take the filter to the sink and give it a good rinse, scrubbing off all that you may deem as dirt and scum. This is a common beginner mistake to make, and it can make your new hobby frustrating because your water will not retain stable levels. The slimy stuff on your media is the good bacteria that is working at absorbing the toxins in your water and filtering it back into clean water. If you wash away all the good bacteria, your aquarium water will suffer until bacteria is formed anew.

Tap water contains chlorine and chloramine that are not really a welcome addition to your tank.

The best way to clean your filter and the media is to use some tank water in a separate bucket or container. Gently clean, but make sure not to scrub off all the slimy stuff. Remember, those are good guys!

Mistake No 7
Fish Need Filtration

If you bought a ready-to-set tank, it surely came with a filter. The most common filtration system to use in aquariums in the 3-step filter. This filter should work fine in the beginning. You may want to eventually change it as you get more accustomed to fish keeping and aquarium cleaning.
It is false to think that any body of water, in any size, doesn’t need filtration. The enclosed environment, no matter how big or how small it is, needs to be filtered for toxins and waste material. Fish simply cannot survive in unhealthy water that is polluted with detritus and toxic wastes.
Adding plants will defiantly help the filtration process, as they absorb some types of toxins and release O2 back into the water.
Shopping for the appropriate filter system for your tank is essential. This is not the place to be stingy if you want to keep a healthy tank with happy fish.

Mistake No 8
Accidental poisoning

Your filter needs to work 24/7. There is no getting around this. No reason is a good reason to turn off your filter. Turning off the filter for prolonged periods of time will provoke dying off of the good bacteria contained inside the filter and media filter. These dead bacteria then turn into toxic and poisonous components for your fish. When you restart the filter, this poisonous substance gets chucked into your aquarium and may kill your fish.
Of course, power outages, and things out of your control may happen. Just keep in mind to cleanse the filter and media before turning it back on. Also, beneficial bacteria may need to be reintroduced into the water by means of liquid or pulverized supplements after a prolonged time with no filter. If you wish to know more about filters, check out here our buying guide.

Mistake No 9
Not Keeping Up Regular Maintenance

Laziness is not a good character trait to have when keeping an aquarium.
Regular programmed maintenance chores need to be scheduled and upheld. Make yourself a daily and weekly maintenance schedule and try your best to upkeep it. If for some reason, it will not be possible to do some chores, have a backup plan.
Having another person aware of the things that need to get dome in your aquarium may come in handy when you need.

Mistake No 10
Don’t Take Tank Advise from Anyone

Some people think that they know everything. They read something on the internet and make themselves the professional know-it-all on the subject.

Trust your own instincts and research for your particular situation.

Also, there is an abundance of forums on the internet where people exchange problems and discuss solutions. The people participating in these forums are usually not trained professionals, so caution needs to be taken when trusting the information that is being offered.
There is also caution to be taken when shopping for your fish and supplies. The store staff may not all be experts and may only be fishing for a sale. It’s always best to do your own research and take advice lightly.

Mistake No 11
Tank Size Matters

You may think that getting a small tank to start will be best.
It’s absolutely false to think that a smaller tank will be easier to care for and ideal for the beginner that you are.

The smaller the tank, the more difficult it is to keep water quality at its best.

The water will go through more fluctuations in a smaller space and be more frustrating for you.
A good starter aquarium size is usually approximately 30 gallons.
We have a detailed post here where we covered the best fish tank size for novice aquarists.

Mistake No 12
Buying Tank and Fish the Same Day

You will absolutely be tempted to get everything up and running as soon as you can. Of course, this is a natural instinct but may mean some frustrations in the near future after throwing everything into a brand new tank that has not been cycled.
We spoke earlier about the importance of cycling the water before introducing new fish.
We can’t stress enough the significance of his crucial step. It is really not recommended to buy an aquarium and the fish the same day.

Mistake No 13

This is one of the easiest mistakes to make when starting out. You are at the fish store and see all those beautiful fish that you imagine in your own tank and get the urge to purchase more than your tank should allow.
The negative consequences are obvious when adding too many occupants to a body of water.
They may go through territorial fighting and of course, there will be more work for you as more fish means more fish excrements.  
There are some rules of thumb to be followed when stocking your aquarium. We have an article on the One Inch of Fish per Gallon Rule rule that is worth reading .
Do the research necessary when choosing your fish and try to avoid the urge to add more fish when you go to the store.

Mistake No 14
Fish Compatibility

One of the most important researches to make when you start your aquarium is the community of fish and inverts that you will choose to create.

You can’t simply go to the store and pick out the cutest fish, come home and throw them all together in your aquarium.

Some fish are territorial and have to live on their own or with their own species, some fish are timid and are not compatible with more aggressive fish.
Different species also have different water chemistry needs, so this has to be considered also. Careful research on your part in these decisions is essential. Websites and even your fish store may have recommendations for you.
Make sure to always check the compatibility of your fish species before adding any new inhabitants.

Mistake No 15

You love your fish and you may love them to death by overfeeding them.
It’s quite easy to give in to their demanding open mouths. Some fish may look like they are constantly hungry, but they are not.

It will take you several weeks to observe the eating habits and keep watch over the leftover food that remains after feedings.

The excess food that fish will not eat in a feeding will fall to the bottom and decay and therefore cause toxins in the water and algae may grow on the glass and decorations.
This means more work for your filter, more work for you, and a possible unhealthy environment for your fish.

Mistake No 16
Obsessing Over Your Fish

When we start a new hobby we want to enjoy every minute of it, right? Well, truth is that your new aquarium probably doesn’t need as much fuss as you will have the inclination to give it in the beginning. Fish are not like dogs or cats that need a lot of attention and care. Actually, your aquarium needs some alone time in order to establish a good stable habitat for your fish. Constantly rearranging things in the aquarium and relentlessly monitoring for problems will create complications that you don’t have and don’t need.

Mistake No 17
Over Medicating

It’s a natural instinct when caring for our pets to make sure that they remain healthy and to care for them when they are not.
Fish health is a little tricky and medications should not be used lightly. It’s recommended that you separate the sick fish into another tank where you will be able to monitor them and treat them accordingly.
Sometimes fish can heal themselves, and other times they need medications. Thorough research is needed when deciding to use medicines with your fish.
Get the right information and make sure to use only the recommended dosage. Over medicating your fish may actually kill them.

Mistake No 18
Appropriate Aquarium Equipment

The most important equipment elements that you will purchase for your aquarium is the filter and the lighting.
These are two essential things that you will choose according to your tank size.
Getting a small filter that is not adequate for your volume of water will mean a lot of work and frustration.
The lighting will also be chosen according to the tank size and fish should have adequate lighting for approximately 8-10 hours a day, or 10-12 for a planted tank.
Check out our Equipment Section where we provide buyer guides on the essential equipment for Aquarium.

Mistake No 19
Using the Wrong Substrate

When choosing the gravel for your new tank, you may have the impulse to choose brightly coloured pebbles that will make your aquarium look interesting.
This is not a good idea as some of these pebbles contain artificial dyes that may be harmful to your fish.
Try to stick with the regular pebble colours that will make your habitat look more environmentally natural.
Medium size gravel is the best choice to make because the larger gravel substrate will amass fish waste and excess food that will, in turn, cause unhealthy toxins to accumulate in the water.
Fine gravel also is not recommended because it causes the water to stagnate at the bottom which can lead to rot and algae growth.
Sand is also a good option. Check out this article on Aquarium Sands if you want to know more.

Mistake No 20
No Plants

It’s easy to believe that plants will be an added chore to your aquarium duties.
This is a common misbelief to make when starting out.

Plants will help remove the nitrates from your water and are a beneficial addition to your tank.

As well as being pleasant to look at, they will keep your water healthy and give your fish a place to play and hide. Here you can find more about plants.

Mistake No 21
Keeping the Lighting on for Too Long

If you have a fish only aquarium, then you probably don’t even need the extra lighting.
Lighting is essential for the plants that are growing in your tank, but your fish most probably prefer some shade.
We want to light up our tank because it looks better and we can see our fish moving around in the water better.
A planted tank will need about 10 hours of light per day, and a fish only aquarium can be lit only when you are home or looking at it.
Using excess light will cause algae growth and this is a major frustration to deal with.
Here is a more in depth look at aquarium lighting and LED Lighting.

Mistake No 22.
Lack of Patience

The number one virtue to possess when starting out on your new aquarist hobby journey.
Lack of patience has to be the number one mistake when starting a new aquarium. It is understandable that you will want everything to happen quickly, but remember that this is a living breathing eco system and it takes time to settle and become stable.
Believe us, you will thank yourself for being patient in the long run.

Good Luck!

Making mistakes is quite normal – it just happens, particularly if you are starting out with a new hobby.
We enjoyed listing what the some of the most common fish keeping mistakes are and hope this will be of help, but there is only one major advice we can provide: research!
Choosing to do some research and making sure that you do the best that you can will definitely improve your chances of surviving that initial start-up period.
Aquarium keeping can be hard work and it is great fun but absolutely requires patience. If you start out well equipped with the proper research and information, then you will minimize your chances of getting frustrated and quitting.
If you follow these simple pieces of advice on how to prevent common mistakes, you will be one step ahead in succeeding at your new and exciting hobby.
We’d love to hear from you in the comments if you have done other mistakes you want to share to help other people to avoid them.