Many beginners will find the similar answer in various articles that a 20-gallon tank is the perfect start for new aquarium hobbyists. And we bet you may immediately wonder why it is not the 5-gallon or 10-gallon but 20-gallon. A little surprise yet you did not read it wrong. Our recommendation is also a 20-gallon tank for general cases. This means… there are certain exceptions that 20 gallons may not be the ideal number for some beginners. 

To figure out why and which case you belong to, let’s go through the sequence of simple questions below. We assure you may grasp a lot of useful information in addition to the suitable tank size for aquarium beginners.

a group of any fish swimming in an aquarium | Splashy Fish

What made you start keeping fish?

Is that because you like a specific fish and want a try? Or simply a lovely aquarium tank for interior decoration? Or more than that, you intend to go for a serious aquarium hobby? To many people, the motivation may be unimportant, but to us, it directs you to the right way at the beginning. That has not yet mentioned it may help you spend less and gain more.


Let’s get started with the first situation that you’ve already decided the fish you are going to keep. As for the case, we are sure you will do the general research for the care guide about the fish in question in advance. On most occasions, a 20-gallon tank appears to be the good choice provided the fish does not possess a large body size and shoaling disposition. For instance, if the fish we are talking about is Angelfish, we’re afraid that an aquarium tank of 20 gallons will not fit them. 

With a unique body shape, Angelfish may need an aquarium of 55 gallons at the least to live peacefully in groups. Further, the tank shape should be high rather than long due to Angelfish’s disc-like appearance. 

Fish in large size require a tank in the similar condition. And keeping fish not only means keeping your pet alive but ensuring it thrives and lives happily. Hence, what you actually need must be both the tank which could fit the fish and the space which is large enough for your fish to enjoy and swim around. Such target is not hard to meet since you have already identified your desire-to-keep fish. Just type their name on Google’s search and figure out the appropriate location in your room to put a fish tank. Then, go with the size as suggested. 

See more: If you are wondering how to determine the right fish stocking for your tank, you could learn about it in our article How many fish should I put in my aquarium?

Koi Angle Fish | Splashy Fish

However, if your cases are the remaining, our suggestion is 20 gallons. The reasons will be explicitly clarified in the following sections.

How many (types of) fish/ invertebrates are you going to keep in the aquarium? 

Depending upon your answer, the tank size could be 20 gallons, or bigger, or even smaller. Indeed, if you keep the nano fish that can live solitarily, you may only need a tank of 10 gallons. This is because fish in smaller sizes do not necessarily need a really big space to thrive. More importantly, they consume less food hence, dispose of less wastes compared to other large fish. This also means you are not required to regularly check the water parameters as well as and perform the maintenance of your fish tank. On the contrary, if you keep relatively large fish in a 10-gallon aquarium, though it is not impossible, you may have to spend more time to carry out these tasks to provide your fish with fresh and clean living environments.

Things are getting complicated when you have yet decided which fish species or invertebrates to be kept. In such situation, we recommend the easy-to-care-for freshwater fish/ invertebrates such as neon tetras, guppy, cherry shrimp, etc. They could help you get a first touch with the common tasks to be done when seriously stepping into the aquarium hobby. Moreover, most of these fish/ invertebrates are also eye-catching hence, no doubt they will give a pleasant vibe for your room.

Nonetheless, this is not over. You could not deny that there is a chance you may want to add more fish after establishing and getting your aquarium tank in good order. This is another crucial reason why you often see the recommendation of 20-gallon fish tanks. If you go for a big tank at first, you do not need to worry about the additional room for new inhabitants. And for those who wish to have diversified fish community tanks, the bigger is always the better.

Discus Fish | Splashy Fish | a community fish tank

Are your fish easy-going in terms of care/ maintenance?

It seems that we are going back to the first issue of whether you’ve decided the fish you want to keep or not. Indeed, if you already made the decision, then go with the suggested tank size you figured out. However, in case you’ve not yet, then 20 gallons is still our answer. As explained for our insistence on such number, we will relate to three crucial matters: health conditions of the fish, water parameters control, and rooms for decorations and required aquarium devices.

  1. Health conditions

Like other pets, fish or invertebrates also love playing and swimming to explore the surroundings during their free time. Hence, it is not fair if you keep your fish/ invertebrates in a space just enough for them to splash back and forth and nothing more. In such cases, fish then feel bored, uneasy and soon get stressed which, suffering for a long period, causes them to be prone to illnesses/ diseases. In addition, some fish are well known for their aggressive temperament and inability to live alone. This means a large area is a must to separate them from each other, hence minimizing the unnecessary fighting as well as their belligerent disposition.

Furthermore, large aquariums allow you to easily create the living conditions that resemble their wild habitats (by adding live aquatic plants or rock caves or driftwoods). This makes the fish feel not only comfortable but also secure thanks to the intimate environments. 

  1. Rooms for decorations and required aquarium devices

Speaking of it, we may mention the matter of the actual rooms that fish/ invertebrates take up. In fact, as for a tank of 20 gallons, it does not mean that 20-gallon is all the space occupied by fish or invertebrates. If you plan to design a lush planted tank, you then need to take room for live aquarium plants into account. If you desire for a diversified aquatic world, beside live plants, you may further need to put rock caves, driftwoods, or other decorations in. This means any time you intend to add a new item to your fish tank, such item will lessen the actual space spent for your fish. Hence, equipping yourself with a large aquarium tank at the beginning will certainly relieve your worry about the additional space in the future. 

Besides, don’t forget the required aquarium devices such as heaters, filters, or lighting systems. Such, subject to the use and design, may need to be equipped within the fish tank. Therefore, they undoubtedly take up another portion of the tank space.

Some may argue that they are beginners and may not likely handle one type of fish well thus, they will not risk taking care of many other (decor) things that appear to be unnecessary. Actually, that statement is not wrong. Many fish could live in a bare tank. However, the more you enhance the aquascapes, the more active and energetic your fish will be. More importantly, the fish tank then will be eye-catching and brighter rather than plain and dull. Since the fishkeeping hobby is a long-term commitment, you don’t need to place everything in the aquarium at the same time. Slowly upgrade it and you will be surprised and well paid for your patience.

In addition, we can assure that buying a large aquarium at the beginning would be better than having a small one to practice then changing to the bigger once skilled. This is because setting up a new well-established aquarium takes a lot of time as well as effort. That has not mentioned the troublesome relocation of the fish to that new tank. With large aquariums, you can earn more than loss, particularly in the matter of tank maintenance.

  1. Easy tank maintenance

Tank maintenance could be understood as keeping and monitoring the tank water conditions in the degrees appropriate for fish to survive. Simply speaking, it includes checking water parameters to make sure they meet the fish’s living requirements, clearing fish’s wastes, and changing water regularly. Due to the purposes, tank maintenance is an unavoidable task that every aquarist must engage if they want their fish to thrive.

The link between tank maintenance and the size of fish tank is that the larger the size, the more stable the water conditions are thus, reducing the times one needs to conduct tank maintenance. Indeed, even if you keep a group of pretty small-sized fish in a big tank, the water conditions are still stable compared to the tank having a large fish. This is because they eat less then dispose less thus, their wastes will not significantly affect the water quality. For beginners, less tank maintenance means less making mistakes and more opportunities to slowly learn and accumulate fishkeeping experience. For fish, less tank maintenance also means less human interference with their lives in new environments hence, causing less stress and worry to themselves. 

On the whole, bigger tanks give better results.

Where is the location you are going to place your fish tank?

This is very important because if you buy a big tank as suggested but don’t have a proper area to place it, that tank will be useless. 20-gallon tanks have many different dimensions. For example, if you buy the 20-gallon tank tall, the dimension would approximately be 24 x 13 x 17 (L x W x H). However, as for the long one, the size would normally be around 30 x 13 x 13. Hence, before considering any fish tank, you should calculate the space that you are going to place your new aquarium.

In addition, do not forget its weight. A weight of a fish tank comprises many things put into that tank, including total amount of water, decorative materials, fish and other living creatures, live plants, aquarium devices. Make sure your ground’s floor is strong enough to support the weight of a 20-gallon tank if that is your choice. If not, there is no other option but the smaller ones.

For more information on the right location to place a fish tank, you could read our article: 

How much will you spend for the aquarium fish tank?

Last but not least, the budget decides everything. The big fish tank always costs more than the smaller ones. If you take the fishkeeping hobby seriously, a 20-gallon tank could not be perfect. However, if you cannot afford one but can be flexible in scheduling your time, then the smaller one is still ok. Tank size is indeed important, but not all the matters. If you have the basic knowledge of what needs to be done before heading to the hobby, we believe you will be alright and handle everything properly.

Splashy Fish Store is happy if the above information is useful to you. Fish-keeping hobby should bring joy rather than concern. We hope this article helps realize and maintain it.

At Splashy Fish Store, we supply a wide range of aquarium accessories which come from reliable sources. We care about the quality and strive to provide you the best we can. Visit our store to find what surprise is waiting for you.