7 Most Common Beginner Aquarium Mistakes To Avoid

Getting an aquarium can be exciting and a lot of fun and to get off with a great start I like to share the 7 most common beginner aquarium mistakes to avoid.

Even though you think you are prepared there will always be a chance in making mistakes. Everybody makes mistakes, nothing you can do about it.

Let’s start with the 7 most common beginner aquarium mistakes to avoid. So you can at least prevent a few beginner mistakes.

1. Cleaning Your Filter Too Often

Your filter is the most important part of your aquarium because millions of bacteria in the filter ensure the breakdown of harmful substances. Your filter ensures the purity of your aquarium water.

When you clean your filter too often you can destroy the ecosystem of your aquarium. There are simply not enough bacteria left to break down the waste of your fish friends. The nitrite levels will peak which can cause your fish friends to die.

One of the most common things to happen with beginners who are too enthusiastic about cleaning their filter and aquarium is a white haze over the water. Wondering what that is? Well, the white haze on top of your water are millions of dead bacteria.Bacteria Because the requirements are very different per type of filter there is simply no rule to follow on how often you should clean your aquarium filter. There are, however, some general guidelines you can follow for cleaning certain types of filters.

  • Under gravel filters are difficult to clean because they are placed underneath your substrate. You still want to aim for every two weeks for basic aquarium maintenance.
  • No need to remove all the substrate you can vacuum your substrate as well.
  • Sponge filters need to be cleaned every 2 weeks to ensure the filter keeps running properly.
  • Hang On filters need to be cleaned once a month.
  • In-Tank Filters are the same as Hang On filters and need to be cleaned once a month as well.
  • Canister filters need to be cleaned every two to four months and can go the longest out of all of them in between cleanings.

2. Adding Fish Too Fast In Your New Aquarium

Without a doubt, the number one mistake everybody makes is adding new fish friends into your aquarium when you get home from the pet store. The worst part of this is, it is not even fully your fault because most pet stores will tell you that the water is suitable which is partly true.

Your water might be ready but your filter is not. Your filter does not have all the beneficial bacteria present and it will take around three to six weeks before your aquarium has finished the cycle process.7 Most Common Beginner Aquarium Mistakes to Avoid - FishingThere is nothing else you can do than to wait until the cycle process has finished.
You could, however, use this time to find out which fish you want for your new aquarium and the kind of requirements they might need. Or just go fishing in the meantime.

3. Changing Too Much Water or Too Little Water

Water changes are healthy because refreshing your aquarium water will replenish the minerals that occur naturally in the water. But if you want to keep your fish friends healthy, changing too much or too little water can harm your fish friends.

When you do not use enough water to change your aquarium water. Your fish friends can die by the chemicals of their own waste. Basically, you are poisoning your fish friends. Plants will use most of the waste products to grow but some of the waste will remain in the water.

Using too much water to change your aquarium water is also not very healthy for your fish friends. You will be removing too much beneficial bacteria with every change. You need these bacteria to convert the waste products of the fish into useful substances for your plants.

By removing too much water there will not be enough beneficial bacteria left to defeat a large number of harmful substances. These harmful substances will also remain in your aquarium and your fish friends can be poisoned.

How much water you need to change depends very much on the size of your aquarium and how many fish friends and plants are in it. A guideline most people use is changing 20% of the water.

4. Over Feeding Your Fish Friends

A common mistake is to overfeed your fish friends. Too much food in your aquarium can be very damaging to the water. Your water values can deteriorate rapidly and nitrate levels will rise. Your fish will produce more waste and the uneaten food will start to rot.

It is a mistake that happens very easily though. Because every time you walk towards your aquarium your fish friends become active and appear hungry. This is normal behavior because the only interaction you have with your fish friends is when you feed them.Over Feeding - Aquarium Beginner Mistakes Why they become active when you come near. Your fish are used to a certain pattern and think they are getting food.

Do not let yourself be tempted in giving them food because they do not need food. Once you have fed your fish a few times and observed them you will quickly find out how much they need. A great guideline to follow is to only feed your fish friends as much as your fish friends can eat. Which is within two to four minutes.

5. Too Much Light Exposure

Whatever you do, do not place your aquarium in direct sunlight unless you like to clean your aquarium a lot. Even with a few minutes of direct sunlight, your algae can grow like insane.

A lot of newcomers into this hobby think they need to follow the natural rhythm of the day and because you want to join your aquarium in the evening too, you decide to leave the light on a bit longer.

When you do this you will expose your aquarium to way too much light and your algae will grow like crazy. You will also ruin the natural rhythm of your fish friends.

Therefore, it is recommended to leave the light on for no longer than 8 hours a day.

6. Aquarium Size

You think you are being smart by choosing a nano aquarium because they are tiny and do not require a lot of maintenance. Well sorry to crush your dreams but it is exactly the opposite. The smaller your aquarium the more knowledge you need because there is simply no room for any errors.Aquarium Size - Nano Aquarium Your nano aquarium is already really tiny and by adding plants and decorations you need to make sure that everything is 100% set up correctly. One tiny itty bitty mistake and the water balance in your aquarium is gone, poof, bye-bye.

Get an aquarium size that allows you to grow into the hobby so you can learn and take action when your aquarium water balance starts to drop or rise. Once you have enough experience you can go for the nano version.

7. Fish Compatibility

Your fish friends must match the respective aquarium (in terms of water values, substrate etc.) and of course, be able to live together. You cannot put every specie of fish together unless you really want an aggressive aquarium.

Fish will eat anything that fits in their mouth even their own young and if you want to enjoy your fish friends you really want to check if your fish are compatible with each other.

Do not purchase too many fish in the beginning. Also, keep in mind that the fish you buy can still grow a lot.


Thank you, everybody, for reading my article about 7 most common beginner aquarium mistakes to avoid.

Hopefully, these tips helped you out a lot but if you have more questions. Feel free to leave them in the comment box below and I will do my best to answer.

  1. Hi Nicole…thanks for these 7 tips for aquarium beginners, returning to my aquaruim after a long period of inactivity….it has only had a couple of live plants in for a number of years, i found that the surface of the water was covered in a white haze and wondered what it was….
    would it be worth me changing the water competely, washing the substrate and filter or changing 10% of the water regularly to prepeare it for some new fish….
    many thanks in advance

    • Heya,

      Thank you for reading my article, glad you liked it.

      It depends on how the white haze looks, if it’s more a cloudy white haze then clean your filters, substrate and change the water fully to start up your aquarium.

      If it looks more like a milky white fog then I would suggest doing a partial water change of 10-20% and get a water test kit to test for ammonia, nitrite, nitrate, and pH levels to keep an eye on the nitrogen process.


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