Depending on how many fish you want to keep or how much space you want to occupy with your tank, you will find different prices. A small, inexpensive, plastic one can be found from 5 GBP up to 15 GBP. If you are looking for something bigger and maybe made of glass, you can find good quality fish tanks from 20 GBP to 60 GBP.
If you want to take your fish and water hobby further, there are fish tanks from 70 GBP up to 200 GBP. Now, if you are looking to become a professional or give a unique style to your home there are fish tanks from 180 GBP, these can easily reach 2800 GBP.
Of course, we are talking about fish tanks that you can buy in different shops, as there are others, much bigger, where you have to hire a professional installation company. These are much more expensive.