Fish tanks can come in all sorts of shapes and sizes. When considering buying your first aquarium I think it is more important to consider the type of fish you are planning on keeping before buying the aquarium itself. Many people will have a space in their house which they wish to fill with an aquarium, which is fine and you can work to the type and quantity of fish to keep based on the size of aquarium. However if this is not the case then decide on the type of fish first and work out the best size aquarium from this.
So if you are planning on keeping some monster fish such as arowana or stingrays then it is just as important to have a deep aquarium as it is to have a long aquarium. For these specific fish it would be recommended to have more than what is seen at the normal depth so 2 foot (60cms) would, by some, be seen as not enough.
It is important to consider the size the fish will grow to, for example the red tail catfish will grow to around 3 foot (90cms) long and will take a relatively short length of time to do so (12-18 months). Although you may see a cute 6inch red tail catfish in your local fish store, consider how big it will eventually get. I would like to think that most stores would check the size of tank you would be putting such a fish in before selling it to you.
If we look at the other end of the scale with smaller fish, for example some shell dwellers from lake Tanganyika which grow no bigger than 4-5cms. If these are the fish you want to keep then it would be pointless buying a large 6 foot fish tank to put them in as it would simply look bare and empty and interest in such a set up would die off very quickly. A nano or smaller tank of around 60 litres would be more than enough to house such a species.
The type and attitude of the fish too, so if you were to go down the route of a cichlid tank with fish from lake Malawi then it would be worth considering how you will stock the tank too. If you under stock the tank then you will likely lose some fish to bullying. We will cover stocking levels and the like in separate post.
Tropical Fish Site has plenty of tropical fish profiles each with the recommended tank size and more relevant information to help you decide and plan your fish tank and what size it should be. These are just guide sizes though and should be seen as such.
Another consideration to take in to account when choosing your aquarium size is the running cost. Although not essential, you will more than likely want to have lighting on for a significant length of time every day an the heaters/chillers and filters must be on 24/7 so the cost of electricity used by a fish tank is quite high. You will of course have the initial outlay of the tank itself, the stand, all equipment plus anything you buy for aquascaping and last, but by no means least – the fish.
When moving in to the territory of a larger fish tank it is worth checking what floor type it will be going on to and how strong this is, the last thing any of us want is a fish tank falling though the ceiling or floor!
In summary it would be best to consider the type of fish you wish to keep and purchase a tank based on this. The initial cost of setting up an aquarium will often seem low but consider everything you must buy to have a design you and the fish can live happily with as well as on going running costs. Please always check the floor will be strong enough to take the weight of the aquarium to avoid massive costs and unwanted puddles in your home.