When I go to the pet store, I see fish tanks that are not only different sizes, but different shapes.

For example, there are tanks that hold the same amount of water, but one could be taller than the other, or one has a bowed front, and there are even some octagon-shaped fish tanks.

Does the shape of a fish tank have any impact on keeping fish inside of it, or is it just for looks?

  • I don't remember what fish it was, but I remember seeing on Tanked that certain fish require a rounded tank so they don't slam face first into walls and injure themselves.
    – Gary
    Commented Mar 21, 2015 at 17:06
  • @Gary I have read once that fish should not live in rounded tanks because they cannot understand their limits. In a rectangle tank they learn the borders because they see and remember some points outside (eg. like the end of bottom layer, stones, sand etc.).
    – Voitcus
    Commented Jun 2, 2015 at 11:33
  • The only fish I know that they purposefully put into round tanks as a requirement are sharks and stingrays. Maybe fish that need to swim long distances can be tricked into swimming in circles. However sometimes the customer orders a round tank and it's never a problem, granted they're large tanks. I've never heard one way or another elsewhere, but they seem to really know what they're doing. Do you remember where you read that?
    – Gary
    Commented Jun 2, 2015 at 20:06
  • @Gary unfortunately, no, I don't remember, but it was a magazine or a website for aquarium enthusiasts, but it was a few years ago. (sorry for answering that late, I haven't realized you asked me - you can use @ sign with nickname to draw one's attention, they will be informed by the system and can respond)
    – Voitcus
    Commented Aug 18, 2015 at 5:23

4 Answers 4


Quite apart from the looks and size, which is how many people select an aquarium, different fish have different requirements.

Some species need a lot of vertical space, others are happy to sit near the bottom or surface all the time. You'll need a higher water column for the first group, for the second you want a larger surface area.

Say you're going for a simulation of a shallow jungle stream, with some bottom dwellers as the main occupants. A large, shallow, tank would be the tank of choice.

If you're going for a steep drop rock slope you want a tall tank but the surface area might be less of a factor.

Of course you're going to need to have proper filtration and aeration in both scenarios.


The shape of a fish tank may influence how you can decorate it. For example a round tank probably doesn't go well with straight edged rocks. As for the varying heights, a tank may be too high to deal with comfortably. On the other hand, between two tanks with the same surface area but one which is deeper, you may want to choose the deeper one as it helps dilute the wastes in the water, provided the fish or other inhabitants can handle deeper water.

Generally, height isn't the most important aspect, as long as it's enough then what really matters is the surface area. A fish probably won't mind being in a round or hexagon tank as long as their is enough space and it is set up appropriately. What you need to consider before buying the tank is how you are going to place the decorations, filters, heaters, and so on.


Yes, it does matter. The primary reason is territory. Many fish are territorial and want to establish their own areas in the tank. The other is swimming space as some fish get stressed out if they cannot swim openly back and forth in the tank. The other reason is lighting. For plant and reef tanks, the shorter the tank, the less light intensity you will need to reach all areas of the tank.

For this reason, the long and shallow tanks tend to be the best choices for fish (rectangle shaped). There are some fish that prefer vertical space, but the vast majority of fish out there are going to prefer a longer tank versus taller.


Yes it matters if I use a bowl for example the surface area of water touching air is poor leading to horrible gas extange and poor aeration also the size matters too depending on the fish I wouldn't put any fish in a tank smaller then 5 gallons

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