How to Care for Your Fish (Aquarium) (with Pictures)

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How to Care for Your Fish (Aquarium) (with Pictures)
How to Care for Your Fish (Aquarium) (with Pictures)

There are fish of different sizes and colors and that's why they are so nice to have at home. Luckily, taking care of them is no biggie, as long as you know how to choose them well and put them in a place with enough space. If you want to have an aquarium, you only need a few basic items, like a filter, and keep it clean and working well.


Part 1 of 3: Choosing your fish and aquarium

Take Care of Your Fish (Tanks) Step 1

Step 1. If your aquarium has a heater, start with tropical fish

Most aquarium fish found in pet stores are tropical, such as tetras, potbellies and betas. These fish need an aquarium with a good heater, otherwise they won't survive. In addition, they are very beautiful and give a look in any environment.

Maintaining the water temperature is very important for this type of fish. Therefore, you should always keep an eye on it, even installing a thermostat

Take Care of Your Fish (Tanks) Step 2

Step 2. If the aquarium has no heat, choose cold water fish

Dorado and minnow are examples of popular species for unheated aquariums. In addition to them, other subtropical and even tropical races also survive under these conditions. Some examples are cobitidae, danio and even crayfish and shrimp.

  • Cold water fish are usually tougher than tropical ones, but they need more space. A well-groomed gold will grow much longer than you think.
  • This type of fish, like the dorado, for example, needs the aquarium water to be always a little cooler than tropical species, staying between 18 and 22 °C.
Take Care of Your Fish (Tanks) Step 3

Step 3. Saltwater fish are more difficult to raise and need more care

If you want to take a risk, know that they are more expensive than freshwater ones and you will always have to be aware of the salinity of the water. Apart from that, raising them requires as much care as any tropical species.

  • Examples of saltwater fish are purple firefish, yellow goby, kleini butterfly fish and angel coral beauty.
  • Over time, metal components will rust in salt water. That's why it's nice to buy equipment made especially for this environment.
Take Care of Your Fish (Tanks) Step 4

Step 4. Choose fish that coexist peacefully in the aquarium

Your first impulse might be to choose the cutest and most colorful ones you can find. But first of all, you need to do some good research to know which species get along well. It is also important to choose a limited number of fish, of just a few species, to avoid territorial and predatory behavior. Fish from the same parts of the world tend to do best when they are in the wild.

  • If you are not sure which fish to buy, ask the pet-shop attendants for help.
  • Beta fish, for example, are very quarrelsome and territorial when they are around other betas, in addition to attacking other species that bite their fins. On the other hand, they coexist well with tetras and corydoras.
  • Goldfish sometimes eat smaller fish than they are. This species does well with the pink barb, cobitidae and danio, but it can still attack them.
Take Care of Your Fish (Tanks) Step 5

Step 5. Choose an aquarium the size you need

Larger ones are much easier to maintain and they are perfect for any species of fish you are thinking of raising. If something goes wrong with the water, like problems with pH, ​​for example, the impact on the environment of larger aquariums is much smaller. In addition, the fish have more space to swim in them.

  • If you're not sure what size you need, choose a fish you like and do some research on it. Bigger fish need bigger aquariums.
  • Small fish, such as tetras and potbellies, for example, need a minimum of 20 liters of water, while a school of fish needs at least 60 liters.
  • Use a 75 L capacity aquarium if you want to breed a goldfish. If you want more than one, add another 40 L per fish.
  • To create a clownfish, use one 40 L. If you want several, buy a 200 L aquarium.

Part 2 of 3: Setting up the aquarium

Take Care of Your Fish (Tanks) Step 6

Step 1. Keep the aquarium away from sources of heat or cold

Temperature changes have serious effects on the water and glass of the aquarium. Therefore, you should avoid placing it near windows, places with drafts, heaters and fireplaces. Find an environment where temperature and sunlight are controlled.

Remember that aquariums are controlled environments. Any small change can have serious effects. Sunlight, for example, changes the temperature of water and can facilitate algae growth

Take Care of Your Fish (Tanks) Step 7

Step 2. Level the tank so it doesn't crack when you fill it

Place it on a stable surface and use a level to see if it is flat. To use this tool, place it over the edges of the aquarium and see if the bubble is right in the center of it. If not, it means the aquarium is crooked.

It's difficult to level the aquarium well. To help, place it on a platform, in a place with a very level floor. Then, go putting wooden shims, in case it is crooked

Take Care of Your Fish (Tanks) Step 8

Step 3. Install the filtering and heating systems in the aquarium

It is necessary that they remain submerged, to regulate the water of the fish, in addition to being suitable for the size of the aquarium. Assemble everything according to the instructions, which is usually not difficult, as you just have to hang them on one of the aquarium walls and plug them in.

  • There are several models of heaters and filters available on the market. Some, for example, ask for the filter to be under the gravel.
  • Heaters are usually adjustable. To find out how hot the water is coming out, turn the lever, adjusting it to your fish's needs. Normally, for fresh water, the ideal is to leave the temperature between 24 and 27 °C.
Take Care of Your Fish (Tanks) Step 9

Step 4. Place substrate and decorative plants in the aquarium

Start by filling the bottom with gravel until you cover it completely. Before placing any ornament on it, wash everything under warm running water and press down well to secure it to the substrate.

  • Add plastic ornaments such as little castles or a pirate ship to add a special touch to the aquarium.
  • When choosing the aquarium plants, think about the environment you want to create. Plants like sinemá, echinodorus, and java fern are great for freshwater tropical aquariums, but they don't do well with saltwater ones.
Take Care of Your Fish (Tanks) Step 10

Step 5. Fill the aquarium with warm tap water and flush the chlorine out of it

As there are no fish in the aquarium yet, you can put the water directly into it. Fill it to the end and then add a little water conditioner, following the mode of use to find the required proportion. When the water is ready, take a little and put it in the filter to make it ready, too.

  • You can find the water conditioner in pet-shops and, as for the dechlorinator, never buy one for swimming pools, always asking for a specific one for aquariums.
  • It is important that the water is warm so as not to damage the aquarium. Don't let cracks in the glass spoil your fish's new home.
Take Care of Your Fish (Tanks) Step 11

Step 6. If the aquarium is for saltwater fish, mix sea salt into the water

Buy one specific for aquariums and follow the manufacturer's instructions to put the right amount. Depending on the product, you will have to add 1.5 kg of salt to every 4 L of water and mix well with an aquarium net or other instrument.

This process must be repeated whenever you add fresh water to the aquarium

Take Care of Your Fish (Tanks) Step 12

Step 7. Let the aquarium run for at least 24 hours before placing the fish

This favors the growth of good bacteria, which are needed to transform the nitrogen produced by fish, food and plants. In addition, there are also others that convert nitrites to nitrates and it is good that they are already well developed when the fish enter the aquarium.

  • If you put the fish in too soon, you will see a sudden spike in nitrogen and nitrates when you test the water, which can be harmful to them.
  • If the fish are from salt water, wait at least three weeks. If you have time, set up the aquarium well in advance, waiting even longer to make sure the environment is safe for the minnows.

Part 3 of 3: Maintaining the Aquarium

Take Care of Your Fish (Tanks) Step 13

Step 1. Feed the fish once a day

The amount depends on the size and quantity of fish, but it's always important to start with little food so that you don't end up eating more than you need. Typically, fish need three to five pellets of feed or a proportionate amount of what comes in flakes. Besides, it's also good to always feed them at the same time.

  • Overfeeding is a serious problem, which can harm the health of fish, who have no control and end up eating whatever is available. In addition, the leftover food ends up contributing to the formation of algae.
  • Find out about the nutritional needs of the species you are caring for, as each is different from the other.
Take Care of Your Fish (Tanks) Step 14

Step 2. Scrub the algae from the aquarium every other week

Buy a proper brush for this at pet-shops, with very stiff bristles and sharp corners to remove even the most stubborn dirt. Clean from the bottom to the top, so that the algae falls on the aquarium floor and vacuum everything up with the siphon. Algae consume the oxygen that aquarium fish and small plants need to survive, so it's important to get rid of them as soon as they start to appear.

  • You can also find magnets for algae. To use them, just hold them against the aquarium lid and suck in the algae as usual.
  • Another way to deal with algae is to put a snail or a fish that feeds on them in the aquarium.
Take Care of Your Fish (Tanks) Step 15

Step 3. Test the pH of the aquarium and replacement water at least once a month

Buy a specific kit for aquariums, which is usually the strip kit, as it is the easiest method, or the common one, which requires the collection of water samples. It is very important to do this test to ensure that the environment is always safe for the fish.

  • Freshwater fish prefer a pH between 5, 5 and 7.5, while saltwater fish prefer the level above 8. Each species of fish has different needs, so it's good to do some research first.
  • Ideally, the water should have zero ammonia and nitrite, and five to ten parts of nitrate for every million parts of water.
  • If your fish are saltwater, buy a kit to test the salinity of the water, which should be 35 g per liter.
Take Care of Your Fish (Tanks) Step 16

Step 4. Remove gravel with a siphon at least twice a month

It is an instrument with long tubes and a vacuum at the tip. To use it, place one of the tubes in a large bucket, used exclusively for aquarium maintenance. Then press the vacuum cleaner gently over the gravel, removing all the dirt, fish feed and algae.

If the siphon ended up taking gravel from the aquarium too, put it back. If it's really dirty, wash it in the same water, but remember to wash your hands first, so as not to introduce bacteria into the tank

Take Care of Your Fish (Tanks) Step 17

Step 5. change up to 25% of the aquarium water fortnightly.

Use the siphon to pass it into a large bucket without taking out the fish. Then replace the water with the same amount you took. If you don't want to waste it, use the dirty water for another purpose, such as watering the plants.

  • The best time to change the water is when you're vacuuming the gravel, as the siphon ends up taking some of it anyway.
  • The idea is to remove 10 to 15% of the water if you vacuum the tank every week.
Take Care of Your Fish (Tanks) Step 18

Step 6. Fill the aquarium with warm, dechlorinated water

But first, put it in a bucket, checking the temperature with a thermometer to make sure it's close to that of the aquarium, then treat it with a water conditioner. For proportions, read the instructions on the product label.

  • Have exclusive utensils to take care of the aquarium. To mix the conditioner in water, for example, the safest and easiest option is to use an aquarium net, which has never been used for anything else. This is important as otherwise you could end up introducing soap or bacteria into the water, harming the environment.
  • If your fish are saltwater, mix some sea salt into the new water, too, following the directions on the package.
Take Care of Your Fish (Tanks) Step 19

Step 7. Rinse the filter monthly and change it when dirty

First, unplug it to turn it off and open it to gain access to the internal components. Depending on the model, you will find either a cylindrical or rectangular cushion inside. To clean it, remove all the pieces and place them in a bowl of water from the aquarium itself, just stirring them a little.

  • This is a good time to check out the filter chamber. If it looks dirty or has accumulated algae, scrub it with a special brush and water from the aquarium itself.
  • If the filter pad is still dirty after water, replace it with another one. You can also tell if it needs to be replaced by noticing the water's circulation speed. If it's too slow, it's a sign that the filter is clogged, but nothing that a little cleaning and a pad change won't solve.


  • When buying fish, be careful what kind of environment they belong to. Knowing, for example, the ideal temperature for each one is very important to make the transition.
  • When setting up your first aquarium, place only cheaper fish, as they tend to survive longer in captivity. If you want to create rare species, get some experience first.
  • Keep an eye out for fish. Changes in appearance or behavior are signs that something is wrong with the aquarium.
  • Start with a few fish and add more according to the size of the aquarium. That way you don't overload the filter.
  • Never try to scare the fish, as stress is very harmful to their lives, even causing them to stop feeding.
  • Always keep the skimmer handy. This tool is great for getting rid of algae and the food the fish have left behind, and it helps to mix dewormers in fresh water.


  • It is not safe to use heaters in aquariums smaller than 9 L, as it ends up slowly cooking fish. The ideal is to buy a big one, so they have plenty of space.
  • The poor maintenance of the aquarium favors the appearance of toxins and algae, which can harm the fish.
  • Some species cannot be together. For the safety of the fish, avoid mixing incompatible species.
  • Don't forget to change your water. If you don't, toxins build up, making the aquarium environment unhealthy and promoting algae growth.

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