What to Know Before Buying Fish – A Complete Checklist

When first getting a fish tank, it’s not like you only go to the store, and get a fish tank and put in some fish. There are a lot more to take into consideration. So, what to know before buying fish for your aquarium?

You need to know what fish to get before buying the equipment to be sure you get the right equipment from the beginning. You need to be sure the water parameters are good for the fish you are getting and you need to have fish that are suitable to live with each other.

Mainly, it is the knowledge you have to get, I have gathered everything other people wish they knew before buying fish and made a guide for you so you can be sure you know everything you need to know. Before buying fish.

What Fish Keepers Wish They Knew Before

Some people think it’s just to get a fish tank, add water, and put in some fish and plants and you’re done. But in reality, it’s not that easy to start a fish tank.

To really know what fish keepers missed at the beginning of their career, I searched the internet and collected data from forums and discussions to know what fish keepers wish they knew before starting to add fish into their fish tanks.

I categorized the information and summarized the result into a pie chart.

The total number of answers I found was 117.

While looking at the chart, what you see is that most people wish they were more informed before buying fish for their fish tank.

This goes hand in hand with the second most common answer which was to cycle the tank before adding fish.

With information, you will know what to do beforehand and you will avoid the risks and problems along the way.

I don’t think reading too much information is going to benefit you because what you will do then is to just keep reading and reading and never get to the point where you actually go out and get the fish.

After all, you will learn a lot by doing mistakes.

With that said, you should not ignore the information either. By getting basic information, you could learn the more common mistakes before they happen and you will find that the fish keeping hobby is much more fun than if you jump straight in without any knowledge.

As you see in the chart, everything is about information. So number one thing experienced fish keepers wanted to know before starting is to read more about the subject of keeping fish.

So let’s start from the beginning, what do you need to know at first?

Before buying anything, you need to know more about the fish you want to put into your fish tank and after that choose the equipment based on the fish.

How To Decide What Type Of Fish You Want

The absolute first thing you have to do before anything is to decide the fish you want in your fish tank.

This is because different fish needs different conditions in the fish tank depending on where they live in nature. Fish are animals and their behavior is also a factor to consider.

Bigger fish will eat smaller fish in nature. This also is the truth in a fish tank. Therefore it’s not a good idea to have a large fish together with smaller fish.

In a fish tank, the space is limited and a bigger fish will most certainly eat a smaller fish since the smaller fish have a lot less space to hide in as in the sea.

This leads to the size of the fish tank. Choosing the right fish for the size of the fish tank.

Right fish tank size

When choosing fish, you need to consider the size. Some fish will grow very big and needs a big fish tank. Others are very small and only need a small tank size.

The size of the fish tank is also depending on where you are going to put it. If you are limited on space where to put your fish tank, you need a smaller fish tank.

With a smaller fish tank, you are limited on which fish to put in. The fish capable of living in smaller tanks can live in bigger tanks too. But fish needing bigger tanks are not capable of living in smaller tanks.

That’s one of the reasons why it’s recommended to keep a bigger tank. You have more options!

Another reason is that a bigger tank is easier to maintain.

If the tank is smaller, if something goes wrong, it will go wrong a lot quicker and it’s less time for you to fix it before your whole fish tank is wiped out.

With a larger tank, it’s easier to figure the problem out before everything living in it is killed.

A drop in the sea is not noticeable, you need a lot of drops for it to be noticeable. In a pond, it will be more noticeable and you need fewer drops to get an effect on the pond compared to the sea.

The difference is that the sea is much bigger than a pond is.

You should also consider the behavior of the fish. more aggressive fish needs larger fish tanks because they need to be able to hide. In a small tank, there are limited places to hide and the aggressive fish might kill the other fish.

Also, you should not add too much fish into the fish tank. The rule of thumb is to add 1 inch (3 cm) of fish per gallon (4 L) of water.

Be sure you count with the fully grown fish. A lot of fish are just babies when being bought in the store so be sure you check their size when fully grown.

Also, be sure to no buy to few of the same species when buying fish. Generally, it’s more harmonic to have a fish tank with more of few species than a fish tank with a few of a lot of species.

I would stick to 2 to 3 types of fish and buy a larger amount of those species.

Water parameters

Depending on where the fish lives in their natural habitat they need different conditions of the water.

The water in the ocean around the world is different. It’s important to choose fish that tolerate the same water conditions.

The main parameters to take into consideration are the pH of the water and the temperature of the water.

You could also decide to make a biotope aquarium. That means that you build your fish tank as if it just from one region of the world. You put in the plants and fish from that region and make the water parameters the same as it is in that region.

You don’t have to do a biotopic aquarium though. There are fish from all around the world that can live in the same environment.

If you decide to choose fish that can live with each other from different parts of the world, you have a community tank that could be very colorful and beautiful.

How To Choose Equipment Based On The Fish

Now, that you have decided what fish to put in, you need to make sure you have the right equipment before putting in fish.

First of all, you need the fish tank itself. Choose it depending on the type of fish that you are going to put in.

be sure the size is sufficient for the type and amount of fish you put in. Also, be sure the place where you put your fish tank can hold the weight.

A fish tank will be very heavy when you put water inside it. The larger the tank, the heavier the tank will be. Be sure you have prepared a space to put it and that you really want it to be. It will be a lot of work to move it later on.

Once you have the fish tank, be sure you have the plants, substrate, and decor. The most important part is to have the substrate in place before adding water. It will be hard to add substrate and make it look nice when the water is added.

Plants and decor are possible and quite easy to add later on but be sure you have a plan on what types you want beforehand. Some fish doesn’t want plants while others want a specific type of plant.

Also, be sure you have the right light for the plants while buying the fish tank.

You should also be sure to have every piece of equipment needed beforehand. What I recommend you to have is

  • A bucket for water change
  • A siphon
  • Towels
  • Water conditioner
  • Starting bacteria
  • Water testing
  • Medicine and activated carbon
  • Fish food

To see what specific products I reccomend, take a look at my Recommended Products page.

How To Prepare The Fish Tank Before Putting In Fish

When you have decided on the fish and gathered all the equipment you need, you need to prepare the tank before adding fish.

As you saw in my study, a lot of people didn’t really know that you need to cycle the tank before adding fish into their fish tanks.

The act of cycling the fish tank is a very important step.

When you cycle the tank you let the beneficial bacteria living in the fish tank grow into a sufficient amount for them to be able to handle the waste from your fish.

To cycle the tank, you should put starting bacteria into your filter and let the fish tank run without any fish inside. Be sure to add a small amount of fish food every day.

This adds food for the bacteria which makes them grow into a sufficient amount. This takes a couple of days but I recommend you to let the tank cycle for a week to be sure the number of bacteria is large enough for them to handle the waste.

In preparation, you should also be prepared to make some maintenance. A water change every week is the most important part of keeping healthy fish.

If you are not sure how to do a water change you’re in luck! I have an article going through every step in the water change. Be sure to read it here while your tank is cycling to be prepared for the water change procedure.

How To Add Fish Into Your Fish Tank

Now the fun part begins, to get the fish from the store!

When choosing a store, you should be picky about where you buy your fish. If the store has algae in their tanks and you see a lot of fish not feeling well you should not choose to buy from that store.

The risk is that you will get a fish of bad quality and it will not survive for long.

A sick fish is a stressed fish and the move from a tank to a new one is adding more stress for the fish which will make it suffer a lot and the fish runs a high risk of dying from stress.

When you have found a good store with good quality fish, you should look out for sick fish. Fish could get sick, even in very favorable conditions. Just as you and I could get sick, even if we live a healthy life.

To see if a fish is a sick look if it’s distancing itself from the other in the tank by staying in a corner. It’s proof that the fish is weak and you have the risk of it getting sick and die in your fish tank if you bring that one home.

Other signs of sick fish are that the fish breath heavily and that its fins are not stretched.

In the fish store, you have the right to chose which of the fish you want.

Also, when buying fish, be sure not to buy too many at the same time. start with about 5 small fish at most. This is because if you add too many fish, the waste will be more, and if the bacteria count is not sufficient enough you run the risk of an ammonia spike which will kill all your fish.

ONce you have bought your fish you will get them in a bag to transport them home. Once home you should add the fish carefully by acclimatizing the fish to their new environment.

If you don’t know how to do it, read my article about it and you will be an expert in introducing new fish into your fish tank.


I have been a fish keeper a big part of my life. During the years I have gathered and searched a lot of information about fish keeping and here, on the website, is where I share that information to help you with your fish keeping. I want to provide the information that I didn't get when I had a question about my fish tank.

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