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20 Gallon Fish Tank Setup Ideas

It is a must for any fish keeper especially beginners to learn the proper information needed before keeping aquatic pets.

Always research before buying materials, equipment, and finally choosing what fish to keep. In doing so this avoids mistakes such as early loss of your fish, improper setup, and others.

A 20-gallon tank is a great starter tank in keeping fish for beginners.

Here are 20-gallon fish tank setup ideas to get you started.

Before you start with your 20 gallon fish tank setup

It is essential to consider factors that can help you set up a great tank. Establish a plan to avoid regrets. The following are 20 gallon fish tank setup ideas one must consider before acquiring materials.

  • Budget- This does not only entail the expenses one might incur on setting up the tank. Consider if you can also set aside a budget for the maintenance of your desired fish habitat.
  • Desired setup- Consider the things you want in your tank, such as plants, decorations and what species of fish you would like to have. Match up your desired setup to the reality of what you will likely have. This is to avoid disappointment.
  • Availability of materials, equipment and fish species- Not all fish species are available at your local pet shop. Some materials or equipment is harder to find in some local places. However, the rise of the digital age has made it easier for anyone to acquire these materials. Materials, equipment, fish, and plants are now available for purchase online.
  • Source of aquatic pets and plants- Scrutinize your sources whether or not they provide healthy and well-kept fish. Some sellers are only in for the profit but provides unhealthy and poorly kept aquatic pets or plants. Ensuring the quality of what you will be paying for makes it easier in maintaining a healthy tank.
  • Good research- It is important to learn the basics and specifics of your desired tank set up. This includes proper set up, proper care for your aquatic pets and proper maintenance. Do not rely on one or two articles, it is always best to read about what you plan to have. Make sure that the source of the information is credible. If possible consult other fish keepers and your local pet shop employees. They can help you better understand fish keeping.

Saltwater vs Freshwater

Video: “Are Freshwater Aquariums Easier Than Saltwater Aquariums?”

Figure out what kind of 20 gallon fish tank setup would you want. The following are differences between a freshwater tank setup and a saltwater tank setup. Knowing the difference between the two will help you determine what kind of tank you should build.


Experienced fish keepers would say that saltwater tanks are harder to set up and maintain while freshwater tanks are fairly easier to set up and maintain. There is truth to this, but proper precautions and proper aquarium setup can make maintenance easier. The average setup for saltwater tanks takes as long as 2 months.

The balance of salt in the water and keeping the plant life healthy are the most significant steps in having a healthy aquarium.

A good fish keeper should thoroughly filter and continuously keep the balance in the water. It is the main reason it is a lengthy process. In doing so, the risk of losing your fish early is lowered.

Saltwater fish are more delicate and cannot easily adapt to sudden changes. Thus the proper setup is a must before adding them in to your tank.

A 20-gallon tank is already considered a small set up for saltwater fish but a good way to start the practice of it. Saltwater pets also tend to be more expensive, this is something you should consider if you wish to set up a saltwater tank.


Keeping and setting up a freshwater tank is easier compared to a saltwater tank. Setting up a freshwater tank with aquatic plants on average can take a month. Non-plant tanks can take at least 2-3 days to set up, although it is encouraged to set up a tank with plants.

Cycle your tank thoroughly before adding in your fish. Freshwater fish are better at adapting to changes, but this does not mean one should ignore the proper ways to set up a tank.

Note: Cost of materials, equipment, the aquatic animals may vary from place to place. Your set up should also cater to the needs of the fishes you have acquired.

Questions To Ponder On Before Buying Essential Things for your 20 Gallon Fish Tank Setup 

How many aquatic animals can I put in a 20-gallon tank? Are they suitable for a 20-gallon tank? Are these species compatible to live with each other?

Depending on what kind of aquatic pets you are planning to keep, it is always best to consider their size. Their size when bought and their size when they mature.

A common example is an angelfish. People often buy this when it’s quite small and put it in a small tank without knowing that angelfish grows into a bigger fish. When they grow big, the small tank will not be suitable anymore. Most owners do not know how to deal with this, and the fish often suffer.

Some fish can thrive in a 20-gallon tank, but some require a bigger space. Search and learn about the species you want to keep. Asking other fish keepers and those working at your local aquatic pet store is a big help.

There are a variety of fish compatibility charts for both saltwater and freshwater pets present in the internet. Observing the tank setups in your local pet shops can help you figure out some of the fish’s compatibility.

Most aquatic pet store employee are knowledgeable of this information. It is best to ask when unsure. Some fish may be compatible to live with other species.

Keep in mind that some fish has the tendency to bully and be aggressive towards smaller species. It is their primal instinct for survival to do so. Building a community tank requires a good understanding of each fish species needs.

Should I put live plants in my tank?

Pick your plants based on the type of fish you are intending to keep. Some plants can thrive in a 20-gallon tank while others require bigger space. Keep in mind that some aquatic animals are herbivores or omnivores and are likely to eat some aquatic plants.

Have I researched enough?

Never limit yourself to one or two articles. It’s always best to have a variety of sources not only from the internet.

Make sure the information you are acquiring comes from trusted sources. Keeping all this in mind avoids the risk of losing your pet and help you do a good job in setting up your tank.

With all this, the following topics are narrowed down to help you set up your tank.

20-gallon tanks are often designed as a decent starter kit or tank for beginners. They often sell this as a kit containing basic essentials to keep you going. However, this is not always the case. In general this kits come in catered for the general species most beginners often pick.

Note: Clean your tank before putting anything in it. Clean both inside and outside of the tank. Wipe it with a damp cloth. Use warm water.

Do not use cleaners with harmful chemicals.

20 Gallon Fish tank Setup Ideas: The Essentials


Have a filtration system. Choose one that best suits your desired aquatic animals. Some filters cause water movement, which some fish do not like. For example tanks with shrimps should have little to no water flow.

Other species like to have water flowing since they are native to rough waters. This can be adjusted by acquiring filters with sponges to help minimize the water flow.

Larger fish also need a filter that is more efficient as they tend to produce more waste. Most filters that come in with a starter kit are decent enough to support the ecosystem of your tank.


LED lights are commonly used as lights for fish tanks. It is durable, effective, and has a low power consumption. Keep in mind that some species prefer dimmer places to thrive into.

When you have a community of fishes in your tank with different preferences, consider their needs. Make sure that in decorating your tank they have a place to hide when the fish do not prefer bright lights. Try lights that closely resembles natural sunlight or moonlight.

Lighting is also crucial in keeping your fish and plants healthy. For saltwater tanks, the inclusion of corals or having a reef tank will require different lighting.

Substrate Gravel and Sand

For freshwater tanks, if you are planning to keep aquatic plants in your aquarium, always have a good aquatic soil. Instructions vary as to how much soil you should put in your tank. In general, around 1 inch of aquatic soil is enough. You can alter it based on the layout you wish your tank will have.

Gravel and sand are also used as substrates, making your tank more pleasing to look at. Following the general rule of thumb, 1 inch of the substrate is enough. But as mentioned, alterations are acceptable, especially when dealing with aqua-scaping.

For saltwater tanks, use substrates to form the seabed. It is recommended to use coarse gravel as it is easier to maintain than sand. Sand is more prone to infestations of critter and bacteria than gravel.

When buying gravel, avoid dyed or painted ones. If you really want them colored then make sure it is nontoxic and won’t have a bad effect on the inhabitants of the tank.

Note: Always clean substrates such as sand and gravel before putting it in your tank. For sand soak it in water and let it settle for a bit, then remove the water. Do this carefully so as to not clog the plumbing lines. For the gravel, wash it a few times. The point of this is to get rid of dust that might have accumulated on the substrate has accumulated display.

Water Heater

A need for a water heater will be dependent on the location of your tank. Water temperature is one of the many ignored factors in keeping aquariums. Most fish has temperature ranges.

The temperature of your tank affects the oxygen present in the water. Beneficial bacteria needs oxygen to break down ammonia which affects the overall health of your fish.

If the area where you will position your tank is quite warm you may not need a water heater. Consider all variables before setting up temperature for your tank.


Having plants can make your tank look more lively and natural. Plants can help in filtering the waste produced by your fish. When buying plants, keep in mind that there are aquatic pets that can eat your plants.

These fishes are herbivores. You can always ask other fish keepers or your local pet shop on what plants are best for the community of fish you are planning to have. Aquatic animals also love having a place to hide, stay into or play in.

Note: If you intend to keep a planted aquarium make sure that natural sunlight can reach your tank if not, you must provide lighting that can cater to your plants. Have a basic knowledge of plant care and maintenance. Taking care of your plants means a healthier environment for your fish.


Stones, pebbles, rocks, and driftwood are the common materials used in decorating tanks. It is important to wash them beforehand, to avoid contamination. Soak driftwood in water before placing them in the tank.

Make sure that the rocks you put in your tank do not have an effect on the water. Especially when your materials are not acquired from shops. Place them strategically to improve the overall aesthetic of your tank. Many tips for aquascaping are online and tutorials on YouTube. Find what best suits your taste.

Now that you have basic knowledge of the essentials let’s further discuss other information you need in keeping an aquarium.

Before buying your Fish

When buying your fish always look for healthy ones. Make sure to buy only from reputable pet shops, those that take good care of the different kinds of fish they sell. It is important because sick fish carries bad bacteria, disease, and other possible infections that can contaminate the tank and affect other healthy inhabitants.

Some pet stores will offer fish that are best suited for your level of skill and help you choose which fish is in prime condition.

The general rules in buying fish are as follows:

  • Do not buy fish from tanks with dead fish.
  • Only buy fish that you are knowledgeable of.
  • They should be swimming properly at the time of purchase.
  • Do not buy from stores that have poorly maintained tanks.

If you are determined to give unhealthy fish from pet stores a better home then that would be all right. But make further research in treating and caring for them.

Fishkeeping is to not only have your aquarium for display but also to provide a good home for your pets.

Consider layering. Some fish are bottom dwellers, middle swimmers, and fish who likes to stay on top. This is to create a harmonious community and avoid overcrowding in the tank. Having more fish occupying the space also adds up to the overall aesthetics of your tank.

Other fish and aquatic animals are helpful in maintaining a well-balanced tank. Such as algae eaters. The production of too much algae can be bad for your tank. Snails and shrimps are great choices in keeping your tank clean and the algae growth minimal.

This is by consuming waste, algae, and others. They must also be compatible with the community you already have in your tank.

Before Adding your Fish

Video: “Adding Fish to Your Aquarium”

Water Salinity

For saltwater tanks, the salt is added to the water and must undergo a series of cycles. Adding table salt to your fish tank is not recommended. Some pet stores sell premixed saltwater. This is to avoid having to go through the tricky process of trying to achieve the right and appropriate water salinity.

Sea salt mix is also available in pet stores. You can also get them from some online stores. They usually come with instructions for you to get the salinity level right.

What kind of water should I use in my tank?

In setting up tanks, do not use tap water. Chlorine and some minerals are not good for your fish and plants. They could be harmful and might cause some serious problems.

Water conditioner are now available in pet stores. Water conditioner get rid of chlorine and alter the condition of the water so fish can thrive.

Cycling your tank

Cycle your tank before adding in fish. Cycling can help you build up beneficial bacteria. Beneficial bacteria are important in keeping a healthy aquarium tank.

Healthy bacteria can help in breaking down the ammonia from fish waste into nitrites and turn those nitrites into nitrates. The difference between the three is the level of harm it can cause to fish. Ammonia is the most harmful and nitrate is the least harmful.

Keeping the nitrate levels of the tank in check is important because having a high nitrate level can cause rapid and massive growth of algae. Also, small amounts of ammonia and nitrites can still be harmful to your fish.


Properly acclimatize your fish. This is a step beginners often ignore. This is why there is an emphasis on research. Do not just put your fish directly to the tank. They need help in adjusting to a new environment.

There are many ways to properly acclimate your fish. The most common technique is letting the bag of the fish float at the side of the aquarium for more than 15 minutes.

By following this process:


Open the bag and pour out at least half of the water.


Secure the bag at the side of the aquarium so that it will not sink or carried around the tank. Make sure that the water from the bag and the tank does not mix.

3Lastly, make sure you do this for just 15 minutes. You can exceed by a few minutes but never more than an hour, before releasing the fish into the tank

The goal of this process is to have the water temperature of the bag with the newly-bought fish reach the same temperature as the water tank. By doing this, it reduces the stress on the fish.

This process helps them calm down. You are also slowly introducing them to their new environment, so they don’t have a hard time adjusting once you put them in.

Failing to do this may cause stress on the fish. Having your fish swimming aimlessly in the tank may also result in injuries or even death.


Setting up your tank especially for beginners is an exciting part of the process of fish keeping. After setting up your tank, remember that you consider proper maintenance and keeping the balance.

Being a fish keeper requires commitment and devotion to the hobby.

Patience is important in having a healthy tank, especially so that the process of setting up your 20 gallon fish tank is a very long process.

Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

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