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Choosing an Aquarium: Top 3 Factors to Consider

Selecting the aquarium which will serve as home for your new fish is an exciting endeavor. Just imagine how it will look when finished, adding that peaceful and exotic touch to the room! Here we will examine the 3 most important factors to consider when choosing your aquarium: size, shape and material.

How to Choose an Aquarium

Home aquariums range in size anywhere from approximately 0.5 gallons up to 200+ gallons. That’s already a wide range of options to choose from! But let’s narrow this down to determine exactly what will suit your goals as well as the needs of the fish.

Small vs Large Tanks

The first thing to know is that the smaller the aquarium, the more difficult it is to maintain at the proper water parameters. For example, the pH levels could swing much more drastically in a 5 gallon aquarium than one with 50 gallons.  The more water quantity, the less effect that any one factor can have upon the whole.

For this reason, a 5 gallon tank should be the smallest freshwater aquarium that you consider. If you’re planning a saltwater aquarium, the minimum size should be closer to 20 gallons. Marine life is generally more affected by large fluctuations in water parameters, so the larger aquarium reduces the likelihood of any one factor causing a material change.

Providing Comfortable Space

Now that we have a minimum, let’s consider the combined size of the fish you wish to include.  The minimum quantity of water should be approximately equal to 1 gallon per inch of fish. For example, if you plan to have 6 fish which total 10 inches in length combined, then you wouldn’t want to place them in a 5 gallon tank.  You’d want to consider 10 gallons or more.

Also consider the characteristics of your fish.  Do a bit of research to determine if any of them need more space than usual, which might be for any number of reasons: a territorial fish, a shy fish who needs room for lots of hiding places, or a high energy fish that prefers more space to swim.

The Base

The weight of the tank will obviously be affected by its size, and that means that the base on which it stands must be strong enough to support it. The water is the heaviest part of the whole aquarium.

1 gallon of water = 8.34 lbs

So if you have a 20 gallon tank, the water alone will weigh something like 167 lbs. Then you have to consider the weight of the aquarium (heavier for glass than for acrylic), along with the combination of decorations, substrate and equipment.

In other words, you don’t want to set this aquarium on a bookshelf or a table!  If you have the ability to check the weight capacity of a potential furniture piece you’re considering, do so!  The larger the aquarium, the riskier it will be to place it on such furniture as a dresser, a desk, or some other object that is not specifically designed to hold such concentrated weight. In addition, such furniture is likely to have water damage or indentations from the presence of the aquarium after some time.

It is generally best to purchase an aquarium base specifically designed for the size and shape of aquarium that you plan to acquire. This provides the most assurance that it will safely be supported.

Why Do Aquarium Dimensions Matter?

Aquariums generally come in a standard rectangular shape, but they can also be cubic or even bowed in the front. Let’s examine each in turn:

Rectangular shape


  • Plenty of swimming space
  • Easy to position equipment
  • Can include a background
  • Convenient for aquascaping
  • Weight is spread over a wider area
  • Light can be more evenly distributed across it


  • Requires more space due to its width
  • Status quo: this is the basic look of aquariums

Cubic shape


  • These can be viewed equally from any angle (no front or back)
  • They are symmetrical, producing a special aesthetic quality
  • Doesn’t require as much width for space


  • Not as much horizontal swimming space
  • Can be more difficult to aerate, filter and light evenly
  • May be more challenging to place the basic equipment
  • Plants and coral may struggle for light due to one overshadowing the other

Bow front shape


  • The curved front is unique and visually appealing
  • It offers a more spacious look
  • You get slightly more capacity in the tank with a smaller floor space


  • This shape often distorts the view of the fish (glass more than acrylic)
  • More difficult to find lights or lids that will fit it
  • The curvature is more difficult to clean than a flat surface

For a comprehensive look at a number of standard and non-standard shapes and dimensions, check out this article from AquAnswers: A Cheat Sheet to Fish Tank Gallon Sizes and Dimensions | AquAnswers

Is a Glass or Acrylic Aquarium Better?

The answer to this question depends on your personal goals for the aquarium. Glass and acrylic both have their strengths as well as their challenges, which we will examine here.

The Glass Aquarium


  • More resistant to scratches, making it easier to clean
  • Maintains its clarity over time without becoming permanently clouded
  • Maintains its shape over time
  • Cheaper than acrylic


  • Weigh significantly more than acrylic, often twice as much or more
  • The larger the capacity, the thicker the glass needed to withstand the water weight
  • Has potential to shatter from high impact incident

The Acrylic Aquarium


  • Far lighter for its size than the equivalent glass aquarium
  • Won’t shatter and is not as subject to breakage
  • Is clearer than glass when allowing light to pass through
  • Higher resistance to water pressure, allowing for thinner walls
  • Better at insulating water temperature
  • It can be formed into many unique shapes


  • Can warp its shape over time due to heavy water weight or high lighting
  • Might experience some yellow cloudiness over time, especially with long exposure to sunlight or other UV source
  • Is more subject to scratching, although minor scratches can be buffed out


When considering what type of tank is best for your aquatic pets, these three considerations of size, shape and material are important to ensure that this aquatic home is best suited to the needs and desires of their fish and human counterparts.

A few questions to ask yourself in relation to the above might be:

Do you have young children or pets that might accidentally scratch or strike the aquarium?

  • Acrylic may be best if there is any remote chance of the aquarium being struck heavily with an object, causing glass to crack or shatter.
  • If scratches are more likely than shattering, you might consider glass.

Is your tank large or small?

  • The larger the tank, the more likely you will want to go with the acrylic option for its weight and its resistance to water pressure.

Is it in direct sunlight?

  • Glass might be the better option so that the UV light doesn’t cloud the aquarium sides over time.

Are you looking for the lowest cost?

  • Glass aquariums are cheaper than acrylic, and easier to clean.

Are you willing to purchase a base for the aquarium?

  • The heavier nature of glass aquariums may make it more likely that you need to purchase a base rather than setting it on existing furniture, depending on the size.

Are you interested in one of the three basic shapes (rectangular, cubic or bow fronted), or are you looking for a more unique or quirky design?

  • Acrylic aquariums can be shaped much more easily than glass, due to its resistance to water pressure.

Final Thoughts

Besides the fish, this is the foundational decision to be made when building your water world. The main thing is that the aquarium be large enough to comfortably support the life within it; the rest really comes down to preference and practicality. The main thing is not to overthink it; simply use this as a guide, and then go for it! As long as your fish have a place to swim, and a knowledgeable owner that can give them what they need, they will be happy as a clam in the mud at high tide! Once you’ve chosen the proper aquarium to meet the requirements of your fish and your selected space, you’re well on your way to transforming your aquatic vision into reality!

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