Aquarium Fish Tank

Beginners Fish Tank – Size Matters

Fish Tank Size Matters

If you know what fish you like and will want in your fish tank, then you need to buy a tank to suit.  You either buy a tank first and afterwards look into what fish it can handle or decide on the fish you want to keep and then pick the right tank size. 

Maybe the size of the tank is set by its proposed location.  In which case the fish selection must be right for the tank size.  Starter aquariums are usually smaller, see our selection of starter kits here.

One of the main reasons anyone wants to have an aquarium is because they really like a particular fish in this case you definitely pick the tank size to suit the breed of fish.

If you aren’t too bothered about the type of fish, then buy the tank that fits the space best.


Should beginners buy bigger fish tanks?

Well this depends on the fish to be kept.  A lot of fish live longer and happier lives in larger tanks with more space.  Some fish get stressed when they feel enclosed and this can cause them to develop a weaker immune system.  Particular types of fish even start to show behavioral issues if the tank size is too small for them.  Our larger aquarium selection is found under the 'Aquariums' heading.

A key consideration for any beginner is getting the water right.  Too often this is overlooked, and the fish don’t survive for long after being dumped in the water and left to get on with it. 

Getting the water balance right for your fish requires you to know what the fish on your tank need to thrive.  This includes the pH level, the water hardness GH, and of course the temperature. There are many great water test kits available to check out the water chemistry.

There is a lot to learn about nitrate and ammonia levels and various other water issues.  For these reasons it can be easier to maintain the water temperature and the right chemistry with larger tanks which can more evenly absorb any mistakes made by the owner in the upkeep of the tank water.  



Small aquarium common problems

  • With less water there can be large rapid fluctuations in water pH and temperature which is dangerous for your fish.
  • Fish produce ammonia all the time.  Even if the filter system is efficient there can be a rapid rise in ammonia levels in a small tank. This leads to an unhealthy aquarium.
  • Smaller tanks with less water surface area than say a long or wide larger tank will have less chance of the air in the atmosphere interacting with the water.  This can result in less oxygen in the water than the fish need.
  • Fish continue can grow lot larger and quickly. In small tanks the growth of larger fish can be restricted causing damage to their health.


Other important considerations when choosing fish tank size:

  • School fish: Certain fish like Rasboras, Tetra, Corydoras are categorised as school fish. They have to be together as a group of at least 5 for them to be healthy and have normal behaviors.  So consider how big 5 fish will be in your tank and buy the tank they need to move around freely.
  • Aquarium dimensions – height is important: For example, angel fish have a peculiar shape. They need taller tanks. Also, some fish like to swim high in the water away from the bottom, these require a tall tank.  To help you understanding how different fish react check out an article about Barbs to get you started.


The tank size really needs to be above the minimum requirement for your selected fish.

If you know the aquarium dimensions input them into an aquarium calculator – we recommend: https://fishtankfocus.com/aquarium-calculator-for-you-to-check-aquarium-dimensions/

This works out the size of the tank in Gallons and Liters so that you know how much water there will be in it. 

Then you can buy filters etc to suit.  It also gives you the weight of common tank sizes, empty and full.

A 30 gallon fish tank is an ideal choice for a beginner.