Buy an aquarium with the greatest amount of surface area. This is where water meets the air. Goldfish would rather swim further (width wise) that deeper. A deeper tank means the water won’t be as well aerated
Goldfish can live for many years and reach their full potential if properly housed in a big enough tank.
It’s important to remember this equation: the smaller the quantity of water in the aquarium, the quicker it will evaporate. You’ll need to top up the water in a small tank regularly, especially in warmer weather.
Tank size and fish
When buying an aquarium take into account the number of fish that you want to keep as this directly affects the size needed.
Goldfish need a clean environment with plenty of room to grow. To the surprise of many people, a 10 to 20 gallon goldfish tank is really only sufficient for 1 goldfish.
Rule of thumb: adding another 10 gallons per fish is ideal.
It’s important to understand that small containers are suitable for a brief time only. Give your pet plenty of space to swim around.
Always use bigger receptacles to house healthy goldfish. Buy the biggest aquarium that you can afford.
Choosing the aquarium shape
There are shape options in patterns and forms available. For example tall, hexagonal, round, square…you get the picture