"I’m looking for something for my little boy who's 5 years old. I realise that I'm the one who'll be properly looking after them, so I’d like something very easy to keep."
Welcome to the start for most fish keepers - something small and something easy! It's worth offering a small warning regarding your first steps into the aquarium hobby, in that it's best to think very carefully before choosing a goldfish. It is an unfortunate myth that goldfish are easy to keep, as they actually need large, well-filtered tanks (which means a larger financial investment on your part), grow to a significant size and have the potential to live for 20 years or more. It is true that once established in the right tank, goldfish are very straightforward in terms of husbandry, but are you willing to properly care for an animal that could potentially see your son graduate from university?
The best fish you can start off with are White Cloud Mountain Minnows or one of the many danio species. These fish are happy in temperate water, which means that there's no need for a heater, and they are also extremely hardy and can be introduced to a tank after a very short maturation time. This can help in handling children's natural impatience to have fish in their aquarium as soon as possible . These fish also remain quite small throughout their lifetime and do not require a huge tank, therefore keeping your fishkeeping costs to a minimum.
It's best to visit your closest Maidenhead Aquatic store so that you can browse amongst the available aquariums and fish. Additionally, any member of staff will be happy to lead you through the basics of fishkeeping and point out any number of different and suitable fish species.
Finally, if you are going to be the primary aquarist, then you should think about what fish you like. By going for tropical rather than temperate fish, you can really expand your options on species that you can keep. The only difference with regards to your initial aquarium costs is the addition of a heater, otherwise the feeding and subsequent maintenance needed for tropical fish are identical to temperate fish.
Guppies, platys are mollies are all excellent fish to start with as they are brightly-coloured, energetic and easy to breed, plus if you find that the fishkeeping bug suddenly bites you, you then have an blank canvas to add more community tropical fish to your tank.